Br 5.4

Please accept this pull request which uses the Tapestry 5.4 require methods to load Google maps javascript and then callback our functions to create the map. I have made these changes on the br_5.4 branch where it looks like you have started making these changes yourself but they were not yet complete. 
I have also updated the Google maps URL for https connections and added ability to set the API key.
Regards
Tim