Updated to latest API

I updated the library to use the latest Digital Ocean API.  Namely Domain support.  I went though the entire API and updated a few functions to comply with the latest API spec.

The only function that breaks compatibility is dropletNew.  They added privateNetworking and backupEnabled flags to the API specification.

I left them in there but I do not think the enable_backups and disable_backups are supported anymore.  I could be wrong but just something to look into. I don't know what the API looked like before now.

I also went though and flushed out the documentation for every function. I mainly just copied/pasted from the API page on the Digital Ocean site.

I noticed that some of the function names are different from the API calls.  I stuck with your naming convention for the functions I added but was wondering if the names you chose had lined up with the old API?  If they should be updated let me know and I can go ahead and do that.