Made colorScheme and typographyScheme properties in the class interfaces for all our examples.
Moved theming away from example inits and into viewDidLoad
Small update for slider example to allow it to grab the theming properly.
Related Pivotal: https://www.pivotaltracker.com/story/show/156616695
Pivotal Story: https://www.pivotaltracker.com/story/show/156168281
* Implementation of Shapes support in Buttons.
* Added example of using shapes on different styles of buttons (see screenshot and gif below).
* Exposed an initializer for MDCCurvedCornerTreatment to be able to use in the example.
* Exposed the color sublayer in MDCShapedShadowLayer to allow hierarchal reordering of sublayers for a shaped button to work with ink and shadow correctly.
* Updated unit tests.
