Merge pull request #269 from Genshin/class_groups

Class groups
[sample] Add sample data for school_years and semesters
[frontend] Fix grade search under class_groups
[frontend] Fix missing fields for birth_date and sex in students show
Merge pull request #272 from Genshin/class_groups

Class groups
[frontend] Prefills enrollment_status_code with enrolled in students new
Merge branch 'master' of github.com:Genshin/GAKUEngine
Update devise to 3.2 and fix after_sign_in redirect
[view] add fiels ESR to view and attendnace_rate method output
[migration] add fields to ESR
[locale] ESR added methods
[model] esr#attendance_rate
[controller] permit more esr attributes
[spec/feature] ESR added columns
[frontend] Fix redirect if not signed in
[migration] remove attedance_rate column
[model] add presence_days and attendance_rate methods to ESR
[spec/model] attendance_rate in ESR
:Merge branch 'master' of github.com:Genshin/gaku into add_fields_to_esr
[view] remove esr attendance rate from student extended search