[develop] Performance Improvements (Markers, MarkerClusterer Rewrite)

Performance tweaks

- lazyUpdate map.coffee
- modelsByRef to disable equality checks
- marker managers improvements (MarkerClustererPlus dropped from google tools sdk)

This is to open up this major PR for discussion how to handle merging in these changes.
@ccg1415 as discussed this would be better to pull in via CoffeeScript as a service or factory. Or I would also recommend to put both of these files (geo-tree.js and this) into a personal repo and push it to bower. Then you can version it and leave it as whatever language of your choice. Then ui-gmap can wrap this as a factory via grunt (like uuid) and not create an external dependency for the user (like bluebird).