The right css file of Exercise 1 (Todos)

[BlackGanglion]

I find the index.css of the exercise one which can't work. A lot of .class should be replaced of #id , so I revise it.

https://github.com/BlackGanglion/Practice/blob/master/backbone-practice/Exercise-1/assets/index.css

[mhenke]

I thought the recommend was not using id - https://www.codecademy.com/forum_questions/50b26dcfa6e5461b2a0003b9

[christianesperar]

This cover on pr https://github.com/addyosmani/backbone-fundamentals/pull/696