Fix paging half-heartedly

This adds paging to the history/ section so we're not displaying *all*
the results.

The paging kind of sucks though since we have to pull back all the results
from redis since they're stored by keys and not by timestamp and we want
to sort them by timestamp before paging.

Two things to note:

1. If someone knows a good way of *not* pulling everything back from redis, that'd be great.
2. I wasn't able to figure out how to test this--it seems like it requires a lot of setup that I can't easily do. I'll write up an issue for that.

r?