Tell segment IO whenever a page is loaded.  Once this works, we
can add more detailed instrumentation for events we care about.

Will be turned off in prod until the SEGMENT_IO_LMS feature flag is
set to True and a SEGMENT_IO_LMS_KEY is set.

Developers can have private settings files by creating
lms/envs/private.py or cms/envs/private.py.  They are imported
at the end of dev.py.  Note that they won't be imported if you
are using one of the other dev*.py variants.

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

* hide the login behind a setting that is turned off by default
* clean out some of the outdated settings and hardcoded test strings

Change the parameters of the sass compiler to output source
maps. Google Chrome uses the maps in the debugger to show the sass or
scss file that originated the style for a particular element.

More information here:

http://fonicmonkey.net/2013/03/25/native-sass-scss-source-map-support-in-chrome-and-rails/

move the instantiation of the metadata cache out of modulestore.py as it was causing a circular import dependency when running on AWS. Put instantiation into one_time_startup.py which I believe is run before any Django requests are handled

optimize forum page rendering as we don't pre-compute the link urls to inline discussions. We can use jump_to urls and then figure out the link path if/when end-user clicks on it. This saves a lot of unnecessary round trips to the DB as path computation is expensive, especially when it being done for every discussion module in a course in a loop.

This reverts commit c4f56620.

This reverts commit ab437b94, reversing
changes made to 7a8e87c7.

- specify mime type
- right urls

Added analytics tab in instructor dashbaord, and call to the analytics back-end to display sample data.

This reverts commit 793354a0.