Added more client apis

Added some more apis that I need to register a domain.

I hope to look into removing Rails as a requirement and standardize responses rather than having to parse the response from Namecheap manually and catch errors.

I also didn't add the users.address API as I wasn't sure where to put it.

Are you looking for a collaborator? Have you tried contacting hashrocket to do a pull request? His seems to have more stars, would be nice to have one that is the main one as it was hard to find when searching.

http://stackoverflow.com/questions/16422457/how-do-i-use-the-namecheap-gem