Copy paste linter-jshint and turn it into linter-jsxhint

It works for me.

Potential questions for the grammars for which this linter should be applied:
* Only 'source.js.jsx'.
* All the jshint grammars and the jsx one?

Solution 1 works great with https://github.com/orktes/atom-react and that is how my editor is configured.
I have not tested Solution #2.

A completly different approach consists of supporting jsxhint from within linter-jshint: https://github.com/AtomLinter/linter-jshint/pull/37
It requires to add to the list of grammars the jsx one and did not feel quite right.