Merge pull request #5 from sdlong/t12087

建立 Group - CRUD 與 RESTful
generate posts_controller without blank helper and scss , js
generate model post and migrate_create_post group_id , content
rake db:migrate migrate_create_post
setting group and post database relationship
group and post model setting vaildates => present
setting posts routes except index and show
posts can show in groups/show
posts/new done
posts/create done
posts/edit and update done
posts/destroy done
posts_controller use before_action => find_group
gem install devise
generate devise install
generate devise user and migrate_create_user
rake db:migrate create_user
generate devise views
controller/posts and groups use before_action => :authenticate_user!
navbar can link_to registration and login