Handle height/width in CommonViewer.

Closes #59 

### File example js533sk1281
![height-width](https://cloud.githubusercontent.com/assets/96776/4686875/41bebbf8-564b-11e4-9f77-cf087e2c87bd.gif)

### Image example cj765pw7168
![cj765pw7168](https://cloud.githubusercontent.com/assets/96776/4687085/53e9a15a-564e-11e4-89ab-b5491dd2b997.gif)