blacklist python-dateutil v2.2 

which suffers from a bug as described at https://gist.github.com/thomasleveil/7274698

Running the Flexget test suite with dateutil 2.2 produces 2 errors and 2 failures ; with 2.1, all pass

bug reported upstream by contacting the author by email
blacklist python-dateutil v2.2 in pavement.py
sync rtd-requirements.txt with pavements.py
blacklist python-dateutil v2.2 in pavement.py (again)
Merge pull request #102 from thomasleveil/patch-1

blacklist python-dateutil v2.2