Update to support enterprise GitHub hosting

This should resolve #7. The initial implementation was not setting the hostname and path on the options array correctly. The resulting values were null when inspected. My corporate GitHub instance is also served over HTTP so I had to introduce logic swap between protocols. Using a different request library other than the node http and https modules could eliminate that switch.

The protocol itself could be inferred if it's preferable to enter http://github.enterprise.com instead of only the hostname github.enterprise.com.