Fixes #5332

This fixes old git_commits_ahead behavior and changes git_commits_behind
to have the same behavior.

Fixes #5355

Changes gke, glol and glola aliases.

Fixes #5362

Confirmed to work on MacOS, OpenBSD, Solaris and busybox.

Refactor of ssh-agent plugin

On systems where the shell cannot be changed because of a strict
security policy, ssh-agent will use the syntax of whatever the
default $SHELL is.
For instance, if the default shell is tcsh, ssh-agent will use the
c-shell style (setenv).

This change forces ssh-agent to use bourne-style syntax since that
has to be later interpreted by zsh. Consequently, the environment
file will contain `export' statements from now on (instead of
`setenv').

This change is important when ssh-add is not inside /usr/bin e.g.
on NixOS.
Signed-off-by: Maximilian Güntner <code@maschinenpsychologe.de>

Coffee was missing an F

Closes #1972.

Repost of #5319 and refactor of rake-fast plugin

This solves a problem of using the variable name `$path' which then
smashes the environment variable `$PATH' and messes up the session.

See https://github.com/robbyrussell/oh-my-zsh/pull/5343#issuecomment-243043098

* Added perms plugin

* HTTPS -> HTTP for comment URL

* Added a README

* Updated TOF comment

* Pulled in updates by apjanke with minor tweaks

Fixes the "syntax error: expected line end ..." (-2741) when using the tab, split_tab and vsplit_tab commands in iTerm2 v3

* updated OSX plugin docs

Clean up Archlinux plugin