highlight use-package before typing package name

This follow the same pattern as the highlighting for provide and require
from `lisp-font-lock-keywords-2' in font-lock.el
Merge pull request #48 from aethanyc/improve-output-buffer

Improve (describe-personal-keybindings) output
Merge pull request #47 from npostavs/hilite-redux

highlight use-package before typing package name