Fix wrapping of "COMMAND LINE" in chrome.

The text "COMMAND LINE" on the Install page is wrapping in chrome. No wrap is occurring in Firefox or IE.

The problem:

![sass install sass](https://cloud.githubusercontent.com/assets/2624149/2933231/277766fe-d7bc-11e3-8158-f0e3a47bec06.png)

Adding a white-space: nowrap; rule fixes the issue:

![sass install sass 1](https://cloud.githubusercontent.com/assets/2624149/2933254/53c56166-d7bc-11e3-95b5-c621fd99f099.png)