Merge rework-inline with rework-import

Here is a merge which bring the following:

* Support media queries
* Add encoding option
* Use [find-file](https://www.npmjs.org/package/find-file) to lookup imports
* Automated tests

@kevva @jxson I've added you guys in the licence & in the package.json.

I want to move this repo into reworkcss org as soon as this pr gets merged.
@jxson are you open to transfert that repo to this organisation ? I will obviously add you & @kevva as maintainers.
Also if you are ok to do that, could you add both kevva & me as maintainers of the package on npm so we can publish ?

I want to go forward with this package to bring relative include asap (I'm preparing this on another branch) to enhance [myth](http://www.myth.io/).

After that @kevva, you will probably need to update rework-inline README to add the merge as a notice to bring rework-inline user to this new merged "official" plugin (under reworkcss org). R u ok with that ?