Better styling syntax

[rtsao]

The current styletron babel plugin is a bit clunky.

A few ideas

1. Just intercept the style prop and use a global singleton styletron instance under the hood
2. Use a "styled-components" helper function

[rtsao]

I'm now thinking option 1 is the better option here since the only time a global singleton is problematic is with rendering within iframes, which isn't really a common use case. Then everything is just plain JSX.