Checking if Content-Type is present in the request headers

[tejinderss]

In decorators.py, there is no check if the Content-Type is present in the headers, which will raise an uncaught exception if we try to use the API in the browser. This check will make sure that the header is present otherwise it will return the json response with 415

[coveralls]

Coverage remained the same at 95.973% when pulling 4f60803 on tejinderss:master into 40d8714 on miLibris:master.

[akira-dev]

You're right. Thanks

[akira-dev]

New release of Flask-REST-JSONAPI is available on pypi with your bug fix

[tejinderss]

Thanks a lot.