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)
Thus far we've avoided using acronyms (or arcane codewords) for services. How terrible would it be to expand this one? `rackspace.NewLoadBalancersV1` as the service-creation function and `rackspace/loadbalancers/v1/nodes`, etc for the resource packages?

On the other hand that would quickly become annoying for the resource packages themselves ("acls" and "lbs", for example). I'm not sure, but I think we already have precedence for using acronyms for resources. I suppose that doesn't bother me as much because at least the acronym is scoped within a specific context and less likely to be confusing.

What do you think?