Trying to make Grunt run jshint again, etc

It seems my Python unit test patch made python tests run, but stopped everything else. Compare

https://travis-ci.org/GoogleChrome/webrtc/builds/42029663 and https://travis-ci.org/GoogleChrome/webrtc.

After some investigation it turns out Travis doesn't support multi-language projects, so we can't run python and npm tasks side-by-side. They're implementing it but there is no ETA.

I'm making the python unit tests manual-only for now; the dev will have to run a script (however it will work to use appengine stubs).