Refactor tests
Create Tag model
Create Questions_tags migration
Make name field of Tags table required
Create Tags controller
Make tags unique
Tag model: green test
Fix factories: tags and questions
Tags controller: green test
Question model with tags: green test
Tag model: class method tests are green
Questions controller: green tests with tags
Tag feature: green tests
Tags finished
Add Tags link to the home page
Improve question CSS
Improve question model for tags
Improve tag model for tags
Improve questions controller for tags
Fix answers and comment controller tests