Version 5.1

Version 5.1 is just released.

Changelog:

• code cleaned
• cluster cursor updated to "pointer"
• allows events and callback to be an array [context, function]
• fix: cast the center if set in option in map function once map is already displayed
• fix: get by id failed when marker in cluster had never been visible
• update kml feature to google.maps version 3.10 + compatibility 3.9-
• fix: clearById + add clear through cluster
• fix: clear directionsrenderer
• fix: multiple infowindow using latLng parameter
• remove a position optimisation on cluster to get faster