Encrypt the session id before writing to tracking logs.
Also use md5 for constructing key for hmac.
Update ddt to 0.8.0
Fixes BLD-1104
Extract i18n strings from *.underscore files using django-babel-underscore
Improve escaping in code response.
Add additional tests for tracking of sessions.
Extract i18n strings from *.underscore files using django-babel-underscore

Change strings from mako.po into underscore.po, which is finally merged into djangojs.po.
Merge pull request #3962 from edx/dcs/BLD-1104

Fixes BLD-1104
Merge pull request #3971 from louyihua/django-babel-underscore

Django babel underscore
extract from underscore files under cms, lms, and common

to avoid extracting from test_root and such
Don't search for underscore files under lms
Babel underscore extraction update according to @nedbat

1. Add underscore.po into the merge section in config.yaml
2. Using one babel command template to construct two babel commands
Merge pull request #3981 from edx/alex/fix_matlab_check

Improve escaping in code response.
Merge pull request #3988 from louyihua/django-babel-underscore

Babel underscore extraction update according to @nedbat
Implement a custom editor for the split_module.

STUD-1529
Text Annotation Tool: Added Instructor Filter and Clear Search
Video Annotation Tool: Added Instructor Filter
Image Annotation Tool: Added Instructor Filter
Image Annotation Tool: Annotation Mode for AB Testing

Annotation Tools PR Fixes

- forgot to overwrite the previous line