Gsmodutils

Model conditions now store objective functions and directions

Added `gsmodutils.utils.design_annoation` decorator for annotating python based designs.
Fixed GsmodutilsModel.save_model for sbml models (it used to save it as a matlab).

The test framework has undergone a significant redesign in this version, though command line and programmatic APIs are maintained with the tester class.

Users can now do a `model.run_tests()` on models loaded into memory that have changes from the filesystem version.

Also minor bugs like cleaning up documentation and adding the rst format for pypi.

First release of gsmodutils on pypi.