Add a compiler plugin for nose.

This is based on lambdalisue's version, but with a couple modifications
to allow overriding preset compiler args and to avoid running doctests
automatically.
wip: try out vim-sexp
wip: add the makegreen plugin
wip: check the error code too, and fix the length of the bar

Note: this requires you have shellpipe setup in such a way that the
error code can get through.
wip: use nosetests for test_*.py files

Requires the machineout plugin.