Moving e2e testing to protractor. See #18.
Checking for application/xml content-type

We need to make sure that the response content-type is checked during
http interception so we don't end up filtering any other response type.
This should now play with JSON and HTML responses.

See #18
When testing the interceptor we should really test if the filter has
been called.
Merge pull request #19 from johngeorgewright/content-type-checking

Content type checking. #see 18