Rackspace CLBs

Addresses #289. Milestones are:

- [x] LBs
- [x] error pages
- [x] LB stats
- [x] nodes
- [x] VIPs
- [ ] domains
- [ ] usage reports
- [x] access lists
- [x] monitors
- [x] session persistence
- [x] connection logging
- [x] throttling
- [ ] caching
- [x] protocols
- [x] algorithms
- [x] SSL termination
- [ ] metadata

(Not sure if all of these resources will make it into this PR)
We ran into this in `objectstorage`. There was a `common.go` file with methods that only seemed relevant to that package. We ended up moving it to `gophercloud` proper (I think in 'results.go`) in part because it was the only package with a file at the root. I *think* both these functions could potentially be used in other packages and, as such, could fit under `gophercloud` proper. That would stay consistent with the other packages and help avoid importing a package called `v1`. Thoughts?