Suggest git.wikimedia.org as httplib2 download site

See Wieland Hoffmanns mail [1] for more details; this should prevent
setup.py install from installing an non-functional httplib2 (that
is: one with outdated SSL certificated)

[1] http://article.gmane.org/gmane.comp.python.pywikipediabot.general/13432

Change-Id: Ia0f91237dde1565a6dd71206c2e0477690cf3855
Merge "Suggest git.wikimedia.org as httplib2 download site"