issue #1027 #1028

- onAdd override was unecessary and incorrect
Merge branch 'issue_1027_1028' into beta

Conflicts:
	dist/angular-google-maps.js
	dist/angular-google-maps.min.js
	dist/angular-google-maps_dev_mapped.js
	dist/angular-google-maps_dev_mapped.js.map
	dist/angular-google-maps_dev_mapped.min.js
	dist/angular-google-maps_dev_mapped.min.js.map
clustering fixes merged