Added analytics event logging to PDF book viewer
Merge pull request #3243 from edx/dcs/pdfbook-logging

Added analytics event logging to PDF book viewer
Add more granular pageview tracking, update Segment.io snippet
Add comments explaining analytics improvements
Remove page view events corresponding to Drupal pages
Multiple-choice features

Features by Jeff Ericson and Nick Parlante squashed
down to one commit.

-shuffle of choices within a choicegroup (Nick)
-answer-pool subsetting within a choicegroup (Jeff)
-masking of choice names within a choicegroup, (Nick)
 used by shuffle and answer-pool
-targeted-feedback within a multiplechoiceresponse (Jeff)
-delay-between-submissions capa feature (Jeff)
Merge pull request #3302 from edx/renzo/analytics-improvements

Add more granular pageview tracking, update Segment.io snippet
Merge pull request #1499 from edx/nick/shuffle-question

Shuffle feature for multiple choice questions
Serve video HTML5 sources locally for acceptance tests
Merge pull request #3331 from edx/zoldak/serve-test-videos-locally

Serve video HTML5 sources locally for acceptance tests