New features?

[KennyGoers]

I was reading over the material design spec and found a few other items that would be useful with this library.

First would be the error or below the edit underline text. A setError/setsubText type thing, essentially a label under as well as above.

Second, the hardcoded 33% transparency works well on dark and light, but I'm using in an instance with a medium dark background and there is no way to change the 33%.

Nice Lib.