Use less disk space for acceptance tests
Merge pull request #14 from edx/gabe/use-less-disk-space

Use less disk space for acceptance tests
Ignore known hosts file for the time being
Grade and "sequentials iewed" distributions from courseware_studenmodule/sqoop
Merge pull request #4 from edx/jbau/grade-distribution-from-sqoop

Histogram statistics tasks from courseware_studentmodule/sqoop exports
Switch to fork of luigi at v1.0.17
Merge pull request #15 from edx/brian/use-luigi-fork

Switch to fork of luigi using v1.0.17
Integrate with opaque_keys package for checking course_ids.

Also change to running Python 2.7 on clusters, since opaque keys
requires that.

* Export opaque keys and dependencies to worker instances in Hadoop.
* Support for checking if course_id is valid.
* Rudimentary support for getting course_id from URL.
* Make sure filenames from course_ids are legal, replacing characters as
  needed.
* Identify organization for each event as close to original algorithm as
  possible on existing data, but working for opaque keys as well.

Acked-by: Brian Wilson <brian@edx.org>
Add more unit tests.
Remove event-export validation code.