Guard, PG, Bourbon, Q

Adding guard to auto-run specs, rewriting specs to use `let` and thus be **a lot** faster. The whole suite runs in 3 seconds now. Also added the ability to edit comments.
So this update made some code stop working. More specifically: https://github.com/eiriklied/commitboards/blob/guard/app/helpers/emoji_helper.rb#L4 Please fix code or downgrade gemoji again. Made a test fail so you see what I mean https://github.com/eiriklied/commitboards/commit/f34b991765e3814089b227dd59421b07c044d233