fix exception in post application/json data

hey guys

while playing with your lib (thanks for that BTW), I noticed that sending data in POST with application/json content-type raises an exception 

    AttributeError: 'dict' object has no attribute 'dict'

I assume it is because restframework is already parsing the request data with default jsonparser, as described [here](http://www.django-rest-framework.org/api-guide/requests). 

removing the `.dict()` call fixes the problem, but I confess I didn't test it extensively

please let me know if it makes sense, I'm running restframework 2.4.3 and django 1.7.1