man page for clinte

Amended Makefile to install said man page.
Explicitly installing files -o root -g root.
allow per-user suppression of clinte notifications

If a user places a file at $HOME/.hushclinte, they will not be
notified of new posts on login.

Moved check logic to a function. Test if .hushclinte exists. If
it doesn't, run the announce function (check_clinte).

Also fixed a shellcheck error - unquoted variable expansion.
Changed string literals to single-quotes.
check if $EDITOR contains flags before calling

If it contains flags, split by whitespace and pass them in as arguments
to std::process::Command. Otherwise, just pass it in as normal. This was
causing a panic/abort.
added removal of notify script to uninstall target
testing for OS to improve portability of new post notification
updated repo location to sr.ht
added sr.ht info to readme

re: sending patches, and build status
added extra newline after new message notification
redirecting stderr to /dev/null

stops an error if a user has never used clinte
removed outdated wording about make behavior
crate version bump
moved hashing to shellscript to check for posts

removes dependency on sha2 crate and allows users
to choose their own hashing algorithm easily.

now copies clinte.json to $HOME/.clinte.json once
the posts are viewed. a shellscript can be used to
compare the hash of the global clinte.json to the
hash of the copy. an example script is supplied.

on `make install` the example script is installed
to /etc/profile.d/, where it will be run for users
on login.
test for hashing bits
recording hash of posts file in homedir

This will facilitate checking for new posts on login.
including manifest for sourcehut builds
removed old packages from travis
changed upgrade steps

changed refs to v2.0.0 -> v2.x
install target: check for clinte.json before copying

removed upgrade target since it's now redundant