Dragging broken - must specify Google API version

[draeath]

I will shortly create a pull request with the fix, but the URL parameter 'v=3.3' must be provided to the Google API call, or dragging-to-pan no longer works.

[draeath]

Please excuse the duplicate PR, I didn't see #20 - however I believe my PR will leave the URL suitable for appending a key, if the user hasn't filled it in in the configuration. #20 would leave it without the version spec in such case, and the end-user wouldn't have any indication it should have been there.