Work on #8

Support Nightly 32 and 33 as a single graph. I think the easiest way to support other channels is to have a little "Nightly/Aurora" selector at the top of the page, since for any given channel there won't be more than one version per build-date.
What if this were more like:
```
document.querySelector("#" + currentChannel).setAttribute("style", "background-color:white");
currentChannel = channel;
document.querySelector("#" + currentChannel).setAttribute("style", "background-color:#90ed7d");
makeGraphsForChannel(currentChannel);
```