Convert to Rails Engine

[mejackreed]

This PR does the following:

• converts gem to a Rails Engine
• Adds in standardized date formats
• Recompiles the fonts in new directory structure (Rails Engine)
• Adds engine_cart for dev and testing
• Creates StyleGuide routes and controllers to test application and for consumers for reference for gem consumers
  • Note routes only get added when not in production
• Adds specs for colors and icons. This way we can make expectations on things that should be present. Hopefully this can help with maintainability for long term.
• Adds travis support

[mejackreed]

Also the styleguide pages you get back look like:

Colors

Icons