Avoid jump caused by recently pushed branches

This is generally useful, but sometimes you can't send a PR _right now_ so it'll keep pushing your content down about a second after page load, messing with your clicks. Perhaps we can make this less intrusive?

<img width="1004" alt="screen shot 2017-12-08 at 17 56 47" src="https://user-images.githubusercontent.com/1402241/33760623-3763b86e-dc41-11e7-90f6-1ae5bf2884ee.png">
