[model] gradable
[concern] gradable
[factory&traits] gradable
[spec/model] gradable
[view] gradable
[controller] set gradable
[controller] to handle gradables
[spec/feature] gradable for exam and courses
[migrate] grading method connector table
[shared example] gradable
[routes] gradable
fix js
[gem] update factorygirl
[helper] improve sortable
Merge branch 'master' of github.com:Genshin/gaku into grading_method_connectors

Conflicts:
	core_dependencies.rb
[model] check for gradable
[spec/model] fix typo
Merge pull request #280 from Genshin/grading_method_connectors

Grading method connectors