Merge pull request #138 from kalkov/develop

merge develop
locale
Merge remote-tracking branch 'upstream/develop'
[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