.brew: Move casks to their own file
.osx: Add threaded email display settings for Mail.app
.osx: Remove old iTunes commands

They only applied to iTunes 10 and older anyway.
.osx: Make coding style more consistent
.osx: Disable inline attachments in Mail

Thanks to Christophe Platteeuw via Twitter: https://twitter.com/cplatteeuw/status/393465401310318592
.osx: Disable automatic spell checking in Mail.app
.osx: Stop iTunes from responding to the keyboard media keys

Commented out, as I actually use these keys.

Closes #265.
.osx: Suppress error messages when running `~/.osx` twice

Closes #266.
.aliases: Improve `ips`

Ref. #268 and #269.