.aliases: Remove things that I don't use
.aliases: Add `jsc` alias

Useful for testing code in JavaScriptCore.

Hat tip: https://twitter.com/RussB/status/420409644117262336 (via @rauschma)
.aliases: Add `afk` to lock the screen
.aliases: Add `reload`

`reload` invokes the shell as a login shell, which essentially reloads it.
.gitconfig: Tweak `status` colors
.gitconfig: Tweak `diff` color