matplotlib 1.2.1 can no longer be downloaded from PyPI.

It is available from source forge but not as a trusted package.  We would either have to upgrade or
download the unverified package.  Looking at the changelog there is only one minor backwards
incompatible change and changes the icon of the diamond in diagrams.
Merge pull request #180 from edx/feanil/update_outdated_requirement

matplotlib 1.2.1 can no longer be downloaded from PyPI.