Fixes pages border so that it fills viewport

Small fix to update this:

![before](https://cloud.githubusercontent.com/assets/354604/4241010/3c59238c-39f0-11e4-8e84-3bd0da4dbf9c.png)

to this:

![after](https://cloud.githubusercontent.com/assets/354604/4241014/41c7bc48-39f0-11e4-8408-901be80460bb.png)