added a sessions controller, added a signin page, need to implement the session storage
added precompiled assets
added the rails_12factor gem
put rails_12factor in one statement
modified the production environment
merged session branch, added a sign in page
to enable asset pipeline, gem rails_12factor is needed
made the email uniqueness
changed all the database into postgresql
Now, users can create a post in the show page
create a post on the user show page
used partial view for sign up form
added a category into post, need to enable multiple categories for each post
deleted an cached file
rebuilt the database using postgresql