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.
small typo: should be _launch_url