Add comment model
Add api for getting comments
Add api for creating comments
Add gray color and less variables
Show comments in hearing page

This is just a raw version. The final version will be implemented
in Angular.
Remove main section from hearing

Simplifies hearing relationships.
Fix image urls
Add user model
Add templates for flash messages
Add auth views and templates
Add like model
Add like_count property to comments
Add API for liking comments
Use english in api urls
Refactor tests
Add tests for model default values
Add likes to comments in templates