.osx: Remove broken three-finger swipe commands

If anyone knows how to make this work, please let me or @necolas know!

Ref. #171.
.osx: Don’t `kill` Dashboard

`killall Dashboard` doesn’t actually do anything. To apply the changes for Dashboard, `killall Dock` is enough as Dock is Dashboard’s parent process.

Closes #277.
.aliases: Add `afk` to lock the screen

Closes #258.
README: Document the `.cask` file

Closes #280.
.osx: Disable smart quotes and dashes
.aliases: Add `reload`

`reload` invokes the shell as a login shell, which essentially reloads it.

Closes #247.
.aliases: Update RubyGems before updating installed gems

Closes #282.
Merge branch 'master' of https://github.com/mathiasbynens/dotfiles

* 'master' of https://github.com/mathiasbynens/dotfiles:
  .aliases: Update RubyGems before updating installed gems
  .aliases: Add `reload`
  .osx: Disable smart quotes and dashes
  README: Document the `.cask` file
  .aliases: Add `afk` to lock the screen
  .osx: Don’t `kill` Dashboard
  .osx: Remove broken three-finger swipe commands