React niceties.

Upgrade to 0.4.1 and show error message on failed compilation.

Test Plan:
* deleted the closing </span> from a file
* ran ./runlint.py over it
* the output included the raw error message from the jsx transformer

* deleted node_modules
* ran ./runlint.py and got a different error message
* ran `npm install`
* ran ./runlint.py again and got no output

Conflicts:
	runlint.py