user role and instance_user role
user role specs
instance role specs
update schema validations gem
Merge pull request #19 from coursemology-collab/wangqiang/basic-roles

basic roles
Use the should_not gem to make sure we don't put 'should' in specs.
Do not start specs with 'should'.
Merge pull request #21 from coursemology-collab/lowjoel/rspec-should-not

Use the should_not gem to make sure we don't put 'should' in specs.
course model specs
implement course model
course_user specs
implement course_user model
course and user relations
Merge pull request #20 from coursemology-collab/wangqiang/course-models

course and enrolment models
install gem cancancan
ability class to handle permissions of admin
Merge pull request #24 from coursemology-collab/wangqiang/authorization

authorization using cancancan