Abstract out the TitleView's implementation

By abstracting out the TitleView's implementation I am now able to drop
in a custom WebView version that allows for some nifty experience in
displaying HTML text.

This includes a refactor to the core where you can override the default
FSTitleView and a sample WebView implementation in the demo project.

There are more changes here than I was originally hoping for, but let me know if you notice anything that is off.