Add a public API to return the definition for a style

I was experimenting with Storybook's jsx addon. Here's its output for a component that's passed an aphrodite style as a prop:

I would like to update the plugin to handle aphrodite styles more gracefully by being display the definition for the rule instead of the aphrodite internals.

Proposed API:
```
function getStyleDefinition(style) => Object
```

Start by tracing Aphrodite's style representation and public exports, then compare the current object shown in the Storybook jsx addon output with the requested definition. Done means a public getStyleDefinition(style) API returns the rule definition rather than Aphrodite internals, with coverage for the relevant style forms.

Written by the indexing model from the issue text.