WIP: ssoma-mda: Translate to Python3.3+, using pygit2 (~0.21.3+)

WIP: ssoma-mda: Translate to Python3.3+, using pygit2 (~0.21.3+)

I'll test with older versions of pygit2 to figure out where the cutoff
is.  And without pygit2 in Debian (even Debian testing), it gets a bit
harder to get this going.  You should be able to use:

  $ apt-get install libgit2-dev
  $ pip install cffi
  $ pip install pygit2

but I haven't fired up a Debian image to test that yet.