Release 0.5.1

This is a maintenance release for the existing components:

• Deprecates TypefaceCompat: your app will continue to compile, however, the Roboto resources have been removed to conserve space and will no longer be applied on pre-Lollipop devices. Use downloadable fonts or FontsContractCompat instead. Thanks to @fountaingeyser!
• Updates support library version to 27+
• Updates AccountHeaderView: you can now build your own account classes based on the IAccount interface. The built-in Account class is still available to quickly get started. Thanks again to @fountaingeyser.

Happy coding!