Rewrite to proxy JSHint options & output.

After working with jsxhint for a while I felt that it could be improved by delegating more of its function to JSHint, rather than providing its own globbing / ignore mechanism.

I figured that in most cases, users will want to use `jsxhint` as a transparent alternative to `jshint`, expecting the same command-line switches & output. It should 'just work' with any libraries that expect `jshint`.

I considered creating a separate repo for this - and I will if you don't want to merge - but since CondeNast controls the `jsxhint` name on npm I figured it best to try to have this accepted as a pull rather than introduce confusion by adding something like `jsxhint2` to npm.

If you are willing to cede the name `jsxhint` on npm please let me know and I would be happy to create a new repo and maintain it.