Fixes XWALK-2756

Code blocks on small screens now used `word-wrap` to fit within a smaller area, less likely to require scrolling:

![screen-shot-2014-10-24-at-6 06 53](https://cloud.githubusercontent.com/assets/1581276/4778285/011bda06-5be4-11e4-9e0e-51fb09dbd897.png)

On larger screens, list nesting is much less dramatic for the sake of the frequently nested docs. Code blocks also are larger than the container as the screen allows, reducing the need to scroll.

![screen shot 2014-10-24 at 1 42 49](https://cloud.githubusercontent.com/assets/1581276/4778283/e84e59e0-5be3-11e4-9b25-f28b2d76ba99.png)