Added xcuserdata to .gitignore

From http://stackoverflow.com/questions/49478/git-ignore-file-for-xcode-project :

Xcode 4 - semi-personal settings, often included in workspaces

You can safely ignore the xcuserdata files - but do NOT ignore the files next to them
Deleted dead code in KCKeyboardTap.m

Brian Hardy identified this dead code in
a17fda4674b470d7ca3f4f00e2c7ce43ee1820bf
Removed code that filtered non-command keystrokes in SvelteVisualizer
Added code to fade the SvelteVisualizer window after 1 second