#3 Update for recent versions of Request

The Requests library made a few changes to its API recently, with the result that pygazelle no longer works with the latest versions of Request published on PyPI.

Specifically, the session constructor no longer accepts any kwargs, you now need to set the properties after instantiation. This patch adapts pygazelle to the new interface.

More info on the API changes: https://github.com/kennethreitz/requests/issues/1131