Support babel 6

[roderickhsiao]

we are not directly require babel in helper, this will prevent user upgrade to babel 6.

Possible remove the jsx-compile function or upgrade to babel 6 syntax

[3den]

@roderickhsiao when i started this project the main goal of jsx-test was to be able to require jsx files on tests, but thanks to babel that is not longer an issue.

I think we should be able to remove jsxTranspile, remove the babel dependency and publish a major update.

[redonkulus]

👍 on that, better to just document that people use babel directly.