Hipchat adapter + Boltdb store

Hi, we've recently started using Victor to power our company chat bot and I've made a few additions with a few more in the pipeline. Our old bot was node.js but I'm learning go and this is a great excuse. 

Speaking of which, I've only been writing go for about a week. This code works for us but I can't vouch for it's purity or adherence to idiomatic go and I'm happy to make changes as needed.

This pull request includes a chat adapter for [Hipchat](https://github.com/abachman/hipchat-go) and a store adapter for [boltdb](https://github.com/boltdb/bolt).
I'm using it as a cached value for the generic Direct regex. I don't know if there's a better way to handle caching/memoizing functions or if I could skip storing this bit and just use `MatchString(d.Direct(".*"), ` down at line 72. I did not check performance but wanted to avoid the concatenation in Direct() from affecting handling since it hits every message that comes through the system.

The greedy handler changes could be safely dropped from this pull request, since Hipchat and Boltdb don't rely on it. It's part of the code we're using right now in our fork, but could be included separately.