Fixes Crashing Bug

Closes #47

The app was crashing because some PubSub objects had a nil caption, which broke the InputSourceManager downstream. This patch fixes that case by guarding against nil pointers in the source manager and verifying the data in the pub sub.
Merge pull request #48 from azoff/47-nil-notification

Fixes Crashing Bug
Addition of welcome controller and animated dismiss.

Now with better transitions!
Merge pull request #50 from azoff/11-feature-welcome-controller

Addition of welcome controller and animated dismiss.
VBNavigationController

Re: #13

- Initial add of basic navigation controller and assets
- Toggle selected state
- Toolbar sliding
- Proper menu sliding state tracking
- Additional view nibs
- Refactoring and use of existing VBColor
- Category in it's own file
- Wire in caption controller and turn off status bar.
- Nib files in project file
- Navigation menu protocol and menu state classes to go with NIBs
- Wiring together navigation controller states with stubs.
- Cosmetic fixes