feature/integrate_auth_lti

Add django_auth_lti icommons library for using application as an LTI tool.  Upgrade version of Django from 1.5 to 1.6.x.  Add a tool_config view for XML configuration endpoint of tool - used by Canvas to determine display of tool link.  Set up "lab" application with it's own urls.py file and include those from top-level urls.py file.  Disable CSRF middleware to allow LTI tool to POST to index view.
This is probably fine for now, but these class constants should be moved out into django settings files.