Modal windows are not scrollable

Created by: sferik

I'm trying to display the "Terms of Service" for a website in a Bootstrap modal box. The length of the Terms stretch the container to be larger than the size of the viewport. At this point, I'd expect the modal box to become scrollable, but instead, it hides the overflown content. Since it's easier to show than to tell, I've attached a screenshot that demonstrates the issue. Let me know if there's any additional information I can provide to help debug. Here's the full code for the project: https://github.com/codeforamerica/adopt-a-hydrant/tree/bootstrap