limit image height on single posts

This is pushing the limits of my css-foo, so a second set of :eyes: would be awesome.

## CF

![screen shot 2013-11-20 at 3 31 03 pm](https://f.cloud.github.com/assets/282759/1586093/bf77a1fe-5223-11e3-8c03-171c6a553c5b.png)

## With

![screen shot 2013-11-20 at 3 38 24 pm](https://f.cloud.github.com/assets/282759/1586094/c36d74f0-5223-11e3-83e5-568711c260cd.png)


Fixes #197.