Implement processor for generating ContentValues.

[ahmedre]

this is a pull request to implement #3 - it adds an annotation processor which generates code for generating ContentValues using a Builder pattern. The Builder is modeled as an interface, similar to the technique used by AutoValue. The @Table annotation is not used right now in and of itself (the processor looks directly for @Table.Builder), but i kept it there based on the assumption that this would expand as time goes on to support some of the other tickets.

[JakeWharton]

Delete file

[JakeWharton]

Mostly just stylistic comments. This is a great start to the processor!

[ahmedre]

I realized now that I jumped the gun a little on this and submitted this request without fully understanding the vision of the project (which I now have a better sense of). In the future, I will propose a solution and get approval on the direction before actually submitting a pull request. I apologize for any inconvenience, and thank you for the review and for providing the community with this library!