Various bug fixes and improvements

[numist]

This branch got away from me a little bit.

• Fixes Raise doesn't always work the first time. #59 - Raise doesn't always work the first time.
• Fixes Selector is not tracking the selected window when it is raised? #105 - Selector is not tracking the selected window when it is raised?
• Fixes Window content workers being leaked somewhere #121 - Window content workers being leaked somewhere
• Better naming for dispatch queues
• Better CocoaPods configuration
• Interface does not show if raise is requested before the display timer has fired
• Thumbnails delay updates at first to reduce system load

[numist]

This stuff should be factored into the state machine. It's conditional on the state machine's state, and is intended to modify a state machine action (displaying the interface).

[numist]

In an ideal world, this will break when #122 gets fixed, as activeApplication should become an immutable data property.

Unfortunately, refreshWindowList won't dispatch a notification if there is only a change in active application, so that'll have to happen later. Sorry, future me.