MUMUP-1209: Use (and add to) Bootstrap 'disabled' class for accessibility

Pretty self-explanatory. 

I also changed the text for the add-more div from 'Click to add more!' to 'Add to your favorites', and gave it better padding.

![image](https://cloud.githubusercontent.com/assets/1919535/4668956/abc14c24-5569-11e4-80da-8cb78c4b0408.png)