Hexdump alias

Custom commands for zim

[history-substring-search] Verify terminfo before bindkey

Closes #341

Update submodules

* zsh-autosuggestions to release v0.6.3
* zsh-completions to release 0.30.0
* zsh-history-substring-search to HEAD
* zsh-syntax-highlighting to HEAD
* lean to HEAD
* liquidprompt to HEAD
* pure to release v1.10.3

Remove cursor highlighter from zimrc template

Not needed in MacOS iTerm and Terminal, (u)rxvt, termite, alacritty and
gnome-terminal.
Does it do any good in any situation?

Closes #337

The develop branch already has this out:
https://github.com/zimfw/install/blob/229cea08e5d2d6806c6bef837d67c2d7a1119744/src/templates/zimrc.zsh.erb#L83-L85

Scope local variable in anonymous function

so it does not leek into the shell.

Copied from zimfw/git@fea95a765558f8efbb039c8e241938fd2bda8954

Update log formats

Use fuller format with committer info instead of medium format, as that
is more complete, and info for author and committer seems to fit in one
line each.

Fix one-line medium format so it truncates the subject at 50, instead of
at the fixed column 60, as that was not good to graph logs.

Remove `--all` from graph log aliases, to increase their flexibility.
We're then able to use it just for the current or for a branch passed
as parameter (as we already could with the other log aliases).

Copied from zimfw/git@63008c817e27dd248a445cac4366f277ae75f0b8

[git] Add aliases for merge sign and verify

Adds the following aliases:
  - gmS: GPG-sign the resulting merge commit.
  - gmV: Verify that the tip commit of the side branch being merged is
  signed with a valid key, i.e. a key that has a valid uid: in the
  default trust model, this means the signing key has been signed by a
  trusted key. If the tip commit of the side branch is not signed with a
  valid key, the merge is aborted.

Closes #333

[git] Allow aliases prefix to be something else than `g`

There were a couple of reports before about aliases shadowing commands
in #59 and #139. And I was impressed to check how many actually shadow existing commands using Ubuntu's command-not-found:

    'gb'  : apt install gb
    'gc'  : apt install graphviz
    'gcp' : apt install gcp
    'gcs' : apt install opengcs
    'gcv' : apt install scotch
    'gdc' : apt install gdc
    'gfm' : apt install gfm
    'gid' : apt install id-utils
    'gld' : apt install postfix-gld
    'gm'  : apt install graphicsmagick
    'gmt' : apt install gmt
    'gp'  : apt install pari-gp
    'gpa' : apt install gpa
    'gpp' : apt install gpp
    'gpt' : apt install gpt
    'grc' : apt install grc
    'gri' : apt install gri
    'gs'  : apt install ghostscript
    'gsl' : apt install generator-scripting-language
    'gss' : apt install libgss-dev
    'gt'  : apt install genometools
    'gtv' : apt install smpeg-gtv
    'gwc' : apt install geneweb
    'gwd' : apt install geneweb

The ability to customize the prefix fixes this issue. Picking `G` for
example is a good one (Vim's Fugitive uses upper case `G` in the
beginning of is commands, to mention another place where it's used).

Closes zimfw/git#1

Copied from zimfw/git@b2a2ffbd3147e2c041eb3b4abcaa17ca2c3454d5

[git] Add `glr` alias for git reflog

and change the commit format to bold yellow, since that's the default
git log format for the commit when colored.

Closes #334

Copied from zimfw/git@013c9d9bf3dc21f3c5841565a8ee300a4e6bfaa7

[prompt] lean: Update submodule

Closes #332

Update LICENSE.md

Closes #322

Update README.md instructions

> You should never have a pipeline both reading from and writing to a file.

My bad. See https://stackoverflow.com/a/25335116/2654518

Fixes #316

[git-info] Add complete example to README.md

so users don't need to look at our prompts code to figure out how having
all the pieces together looks like.

[prompt] eriner: Fix ${USER} not being evaluated

I broke this on the last commit. My bad.

Fixes #318

[git-info] Document that flag (e) is needed

so proper expansion of ref names occurs, due to changes done in 53a3cd7.

Update modules' README.md

Stick with the following style:

* Header 1 with the module name is in `lowercase`.
* Other headers are in `Sentence case`. Common header names that should
  be consistently used are `Aliases`, `Contributing`, `Functions`,
  `Settings`, and `Zsh options`.
* The names `Zim` and `Zsh` always appear capitalized, even in the
  middle of sentences.
* Prefer

      print 'code indented with 4 spaces'

  instead of
  ```zsh
  print 'code fenced by lines with three back-ticks'
  print 'unless you want syntax highlighting'
  ```

[completion] Add options to README.md

Prefer `setopt NO_FOO` instead of `unsetopt FOO`, as former is easier to
document in the README.

Stick with the following style for the README:

* Header 1 with the module name is in `lowercase`.
* Other headers are in `Sentence case`. Common header names that should
  be consistently used are `Aliases`, `Contributing`, `Functions`,
  `Settings`, and `Zsh options`.

[history] Use fc -l instead of history

`history` is equivalent to `fc -l`, and `fc` is the actual Zsh builtin.

Add the `-n` flag to suppress event numbers when listing.

[history] Remove EXTENDED_HISTORY and INC_APPEND_HISTORY

as they are not required (not even recommended) to be set along with
`SHARE_HISTORY`. See zshoptions(1) on `SHARE_HISTORY`:

> This option ... also causes your typed commands to be appended to the
> history file (the latter is like specifying `INC_APPEND_HISTORY`,
> which should be turned off if this option is in effect). The history
> lines are also output with timestamps ala `EXTENDED_HISTORY` ...

Also update copy in comments and in the README. Stick with the following
style for the README:

* Header 1 with the module name is in `lowercase`.
* Other headers are in `Sentence case`. Common header names that should
  be consistently used are `Aliases`, `Functions`, `Settings`, and
  `Zsh options`.
* The names `Zim` and `Zsh` always appear capitalized, even in the
  middle of sentences.

Closes #313