Version 2.0

There are a number of things I'd like to accomplish with a 2.0 release:

- [x] Deprecate Ruby 1.8.x
- [x] Update versions of all supported endpoints as applicable
- [ ] Persistent HTTP connections (https://github.com/soupmatt/persistent_httparty ?)
- [ ] Investigate other HTTP libraries altogether. HTTParty is great and all but others may be better for our use case.
- [ ] CloudFront and Signature Version 4 support #18 
- [ ] Internal support for IAM Roles
- [x] Fix sort issue with X-AMZ headers #14