Fix for templates missing on install of XBlock.

Fix for templates missing after install.

Modified:
setup.py to include templates dir in package_data
sga.py from get_template to render_template
tests.py to fix resulting broken tests

I know it is a bit of a nit pick, but do you mind leaving these multiple spaced (or at least 2 via pep-8)? I know there are a bunch of other little violations, but it would be nice not to add new ones.