Fix bug on using requests 1.0.4

Method requests.session() has no arguments on requests 1.0.4. They have removed them on commit https://github.com/kennethreitz/requests/commit/6acce57271efce8c17cea2f1eece943f429e3879#requests/sessions.py
Merge remote-tracking branch 'mativs/master' into dev

Conflicts:
	slumber/__init__.py