Wrong expectation for default Content-type on POST requests

[joyously]

bliss/tests/objects/FetchSpec.js

Line 39 in 6bd9c06

it("sets Content-type header for POST if not provided", function () {

This test case is faulty. Not all POST requests should have the same default Content-type.
If you look at this example, and try to code that with fetch instead, it won't work correctly (file is not uploaded).
This covers up a bug with fetch.