Avit theme fixes

Optimize the ys.zsh-theme make it more expressive

Update kennethreitz.zsh-theme

$CARETCOLOR was not to actually colour the caret, so change to root user
wouldn't show in the prompt. Now both ▶ and ◀ follow $CARETCOLOR.

Make some colours in the avit theme bold for better visibility in the
default Ubuntu terminal theme.

Fix bug in compass docs search

fix terminal color pollution

Close #2452

Update -> upgrade
Erase -> remove

Adds some useful aliases

git.plugin: remove the conflicting gvt alias

See FiloSottile/gvt#19 and FiloSottile/gvt#4

Update _brew to match latest

Updated _brew to match latest in https://github.com/Homebrew/homebrew/blob/master/Library/Contributions/brew_zsh_completion.zsh

pylint.plugin.zsh: Remove include-ids=y

The flag `--include-ids` is soon to be deprecated for Pylint. This pull request
removes that option from pylint-quick

Also, fix a couple of typos / style issues.

Close #4723

Seems like this is more like the intended effect, splits arguments with commas
for proper gitignore.io api request.
Thanks for teaching me about custom compdef completions!

Updated with zsh join operator by Marc Cornellà

Close #3747

znt: optimizations for zsh<=5.2

Vault basic autocompletion

forklift: update homepage URL and tweak formatting

Add OSX support for command-not-found

chruby plugin locals moved inside function