Send request data as JSON

I haven't tested this---I'm having trouble duplicating my old virtualenv on my new install...

This should be merged at the same time as https://github.com/CCI-MOC/moc-rest/pull/2
I don't see any benefit to that besides line length.  The way I wrote it is simple and obvious. Even the people writing the official requests tutorial don't use it:

    >>> body = json.dumps({u"body": u"Sounds great! I'll get right on it!"})
    >>> url = u"https://api.github.com/repos/kennethreitz/requests/issues/482/comments"
    >>> r = requests.post(url=url, data=body)
   >>> r.status_code