Speed up bundler in Travis bootstrap

* Add -j4 option for speed up
* Add --quiet
* Add development ENV into exclusion list
Merge pull request #283 from joneslee85/patch-1

Speed up bundler in Travis bootstrap
Get rid of set_default_language callback for User

This would gain following:

* Make it easy for developers to extend or change the User Creation process
* Easier to create test factory and to test
Get rid of deprecation warning for Gaku::Semester.with_class_group scope
Merge pull request #284 from joneslee85/refactoring-user

Get rid of set_default_language callback for User
Merge pull request #285 from joneslee85/patch-1

Get rid of deprecation warning for Gaku::Semester.with_class_group scope
Add sample data for applicant students
Merge branch 'master' of github.com:Genshin/GAKUEngine
Fix header
Merge branch 'master' of github.com:Genshin/gaku into exam_sessions