* Add unit test coverage for this "exclusion from tracking" logic
* Exclude based on regex match instead of raw string comparison
* Exclude heartbeat requests from tracking

Also added datadog application to commom django apps and set it to use
a local statsd server by default.

not common.  This ensures that we load the MITX_FEATURES
token BEFORE deciding to disable CSRF.

to cms settings (it was throwing 500s for Stanford when the CMS
calls render_from_lms)

allow configuration settings to specify a session cookie name. This is to avoid problems we are experiencing between simultaneous login sessions between edx.org and edge.edx.org on certain browsers (i.e. Firefox)

PREVIEW_LMS_BASE must now be set (default value does not work for both edge and edx). Make this work locally as well.
https://edx.lighthouseapp.com/projects/102637/tickets/331

Start linting envs files, add task to only pylint errors, and move pylintrc file to the correct location