Resolve #39, support React Components composing

[lttb]

From #39

import React from 'react'
import styled from 'styled-jss'

const Test = (props) => <h1 {...props}>test</h1>;

const StyledTest = styled(Test)({
  padding: 40,
  background: '#f7df1e',
  textAlign: 'center'
})

const Root = () => (
  <StyledTest />
)

export default Root

[coveralls]

Coverage remained the same at 100.0% when pulling c3577a6 on feature/compose-react-components into 319c17d on master.