fix git_export tests

fix pep8 violation

Fix typo in cms unit test

fixes failing unit test in course_groups

Update pep8 to 1.5.7

Change openedx footer image to a non-broken link

Implements keyword sub feature for bulk emails

Check settings.FEATURES["ADVANCED_SECURITY"] first

Don't break up i18n string

Unit test speed improvements

Fix white spaces inside navigation

WL-105 Show course cards sorted by start dates, oldest first.

This commit pulls in changes from #4487 that implements keyword
substitution for bulk emails. With these changes, an instructor can
include keywords in their bulk emails which will be automatically substituted
with the corresponding value for the recepient of the email. Keywords are
of the form %%keyword%%, and the keywords implemented in this commit include:

%%USER_ID%% => anonymous_user_id
%%USER_FULLNAME%% => user profile name
%%COURSE_DISPLAY_NAME%% => display name of the course
%%COURSE_END_DATE%% => end date of the course

Client-side validations have also been implemented to ensure that only emails
with well-formed keywords can be sent.
The architecture is designed such that adding in new keywords in the future
would be relatively straight-forward.

Limit Upload File Sizes to GridFS

hotfix-2014-12-11

We do this intentionally, to preserve tracebacks

Update pillow to 2.6.1

MA-182 Fix Mobile Subtitles.

round-off weight value while returing grading policy

TNL-884

moving defaults for yaml config out of common.py

This reads configuration directly from yaml
and imports it directly into settings