Add test for number of microposts and pagination on home page. (exercise 10.5.1 10.5.2)
Add partials to the home page. (exercise 10.5.3)
Add tests for checking the delete links. (exercise 10.5.4)
Split partial from feed_item and micropost. (exercise 10.5.5)
Add word length restliction. (exercise 10.5.6)
Add relationship model. (11.1.1~11.1.3)