* fix type mismatch in course_goals migrations
* fix type mismatch in experiments migrations
* fix type mismatch in xblock_django migrations
* fix type mismatch in catalog migrations
* fix type mismatch in static_replace migrations
* fix type mismatch in bulk_email migrations
* fix type mismatch in course_overviews migrations
* INCR-248: Make compatible with Python 3.x without breaking Python 2.7 support --> common/djangoapps/xblock_django
* INCR-248: Grouped absolute_import and unicode_literals imports
* INCR-248: Grouped absolute_import and unicode_literals imports for migrations