Scaffold main_concept and sub_concept, remove migrations
Update models
Run migration for concept inheritance
Add column parent_id to concepts
Update views considering inheritance
Merge branch 'concept_inheritance' into develop
Merge branch 'hotfix' into develop
Bundle devise and cancancan
Configure devise
Create User model and migrate db
Generate cancan:ability
Activate cancancan
Add column admin to users
Add sign_in and logout to navbar
Bundle gems for Heroku
Set database settings for Heroku
Merge branch 'develop'