[controller] group courses by semester and courses without semester
[helper] making universal helper for extracting resources form join model grouping
[model] scope courses without semester and class method for grouping courses by semester id
[views/js] refactor views and js for grouping courses
[spec] refactor specs to match  grouping for courses
[spec/model] test for dependency destroy
Update travis, leave only postgresql as test DB
Merge remote-tracking branch 'upstream/master' into develop
check for right assigned insta variable for class group and courses controller
changed ruby version to 2.0.0
Merge pull request #150 from Genshin/fix_course_and_class_group_controller_spec

check for right assigned insta variable for class group and courses cont...
Merge remote-tracking branch 'upstream/master'