.osx: Remove “Enable access for assistive devices”

This feature doesn’t work anymore in OS X 10.9 Mavericks. The setting has moved to System Preferences → Security & Privacy → Accessibility, where you now have to check every app you want to allow access rather than enabling it globally.

Closes #262.
.osx: Use plain text smileys in Messages

Messages in OS X 10.9 Mavericks automatically substitutes e.g. `:)` with `😊`, with no way to disable this feature through the app’s preferences pane.

After analyzing the `defaults read` output it turns out there is a hidden preference for it.
.osx: Consistently specify the type for `dict-add` actions
.functions: Add `tre` shorthand

Closes #249.
.osx: Disable smart quotes in Messages.app
.osx: Disable continuous spell checking in Messages.app
.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.
Make `.cask` executable
.osx: Minimize windows into their application’s icon

Closes #271.
init: Add iTerm colors

Closes #274.
init: Install Sublime Text settings

Closes #275.
.osx: Rename computer name