zsh: make the rfc cmd just launch the vim plugin
git: remove glog alias
mutt: change editor tw from 80 to 72
notmuch: use absolute path to mail dir

Relative paths work on Linux, but not macOS for some reason. Since
there's no harm in using absolute paths everywhere, change the file to a
template and inject the current user's home directory as a prefix to the
mail directory path.
vdirsyncer: set conflict resolution to use remote
mutt: set edit_headers=true
mutt: don't set unneeded sort_aux
git: enable rebase.autoSquash
vim: add vim-rfc plugin
zsh: update CDPATH

Sometimes it's hard to figure out where exactly in the GOPATH a
repository should live when there is not necessarily one canonical
remote. Now that Go supports modules outside of GOPATH, I think I'd like
to move away from keeping everything in code/src/ and simply keep
repositories in a top-level directory. Eventually, I think I'll want to
rename the directories:

    code -> go
    c -> code

But as this is relatively experimental for me currently, I'm holding off
on that and just updating CDPATH.
[zsh] fix environment secrets

GITHUB_TOKEN is actually in .localrc, and
PASSWORD_STORE_GENERATED_LENGTH isn't actually a secret.
[vim] add prettier
[bin] Add rot13 program
[tmux] show status on Darwin
[zsh] consolidate darwin/freebsd aliases
[java] use homebrew java 8 rather than java 11
[zsh] remove infrequently-used aliases
[bin] update extract script, alias to x
[zsh] remove `rp` alias for `hub pull-request`

The `rp` script was a lot more useful when it actually built the summary
based on the git log and interacted with the Bitbucket API, but now that
it does not, this doesn't really need to be a whole unique function.