Support "css"-property for {"mode": "classNames"}

[danielberndt]

Currently this won't work with non-plugin emotion:

const MyComp = glamorous.div({})
<MyComp css={{color: "red"}}/>

it will get translated to

const MyComp = styled("div")({})
<MyComp css={{color: "red"}}/>

but the css prop won't be handled by emotion.