Modified base function to have explicit flag to remove marker from map while removing from cluster management;

-no mention in documentation that marker is removed from cluster mangement AND map;
-inflexible to handle certain use cases when markers are only needed to be unclustered yet still remain on map
Added option to prevent marker removal from map while removing from cluster management;

-leverages change in base removeMarker_ function
-preserves previous functionality method invocation to provide legacy support
Updated function documentation for marker removal;

-educates about new function option
-explicitly states the default removes from cluster management and from map
Merge pull request #3 from Juicetan/develop

Add option to remove marker from cluster but still remaining on map