Support Annotations in generated code

[ZacSweers]

From @hzsweers on September 1, 2015 21:54

Hacked at this for awhile and can't for the life of me get it to work.

Adding a dependency with a local maven URL (as per the docs' suggestion) doesn't work because it still can't find it.

Adding the jar works, but doesn't get included in the packaging for some reason.

If we do add this though, we would want the following:

• All put() methods would have @CheckResult and @NonNull annotations
• All rx() methods would have @CheckResult and @NonNull annotations
• All put(String) methods would have @Nullable annotations on the parameter
  • This applies to future object types too

Copied from original issue: Flipboard#1

[ZacSweers]

Possibly related issue: JakeWharton/butterknife#362

[ZacSweers]

I know how to do this now, will work on it when I'm back from vacation