Merge pull request #2 from scragg0x/master

Added options to getLoginUrl
Added getLoginUrl to docs
Added getFriends, /friends/{service} endpoint.
I noticed zend\http\client::setParameterGet s explicitly set Get params rather than append any that have been previously set.
So I went ahead and corrected where it was used this way.
I removed versions from the URL, I think we can add that later if Singly comes up with a new version.
I set parameters in function arguments as parameters = array() rather than null to hint at expected type in IDEs.