vellum changes

Update to built version of latest master of http://github.com/mwhite/Vellum, which fixes all issues I'm aware of.  As in, I think it's production-ready if you can't find any more bugs.

Process as described in the README there is to download an automatically-built archive of the built files from drone.io and extract to a folder in HQ.  As in, this removes the Vellum submodule, without adding anything to the HQ build script.

If you change `{% if false and debug %}` to `{% if debug %}` in `form_designer.html`, you can run the non-built version of Vellum in HQ.  It's expected to be cloned in a directory next to the commcare-hq root. (Perhaps it would be good to add a vellum_debug setting which defaults to the value of DEBUG to avoid having to make this change every time.)

However, seeing as basically everything except uploading multimedia and saving a form to HQ can be tested in the test page, I highly recommend just using that.  It's still deployed automatically to http://vellum-master.herokuapp.com and on pull requests.  It defaults to using the non-built version on localhost and the built version otherwise.  You can override this by appending ?built or ?async.  Will make some links for this on the test page.

There are a few minor non-blocking issues with the RequireJS setup that should be addressed at some point: https://github.com/mwhite/Vellum/issues/112

I've enabled Travis on my repo with just JSHint for now, and will be re-hooking up the existing tests once I write some tests for my upcoming changes.  

Hopefully now we can switch to doing incremental PRs off my master, which can get acceptance testing on the PR, and which I can then review pretty effectively for defects since I've read and touched the entire codebase many times by now, and then you can do whatever you want for regression testing and submit bugs as Github issues.