cloudconnector: onedrive replaces skydrive

* OneDrive is the new name of the service previously known as SkyDrive:
  https://github.com/mk-fg/python-onedrive/commit/a69252e

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
installation: Pillow instead of PIL

* Deleting PIL since Pillow replaces it and PIL doesn't resolve anymore
  on PyPI. NB: Ubuntu and Debian python-imaging package uses Pillow.

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
travis: extra requirements to tests

* Adding -img and -extras to the installation process, so if anything
  break, we might get notified.

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>