fix(marker): markers now update on model changes

motivation: markers update relies on a comparison between a cached (cloned) version of the
model and the reference model. Prior to this commit, the cached model is built using a shallow
copy of the reference model (using `_.extends`). Thus, both cached and reference model properties
are always identical and model properties changes, e.g. coordinates, are not reflected on the map.
In this commit, the cached model is built using a *deep-copy* using `_.clone(model,true)`.

solves issue #1350

src/coffee/directives/api/models/child/marker-child-model.coffee

@@ -23,7 +23,7 @@ angular.module('uiGmapgoogle-maps.directives.api.models.child')
         @trackModel = true, @needRedraw = false) ->
         #where @model is a reference to model in the controller scope
         #clonedModel is a copy for comparison
-        @clonedModel = _.extend({},@model)
+        @clonedModel = _.clone(@model,true)
         @deferred = uiGmapPromise.defer()
         _.each @keys, (v, k) =>
           keyValue = @keys[k]
@@ -80,7 +80,7 @@ angular.module('uiGmapgoogle-maps.directives.api.models.child')
             @needRedraw = true
 
       updateModel: (model) =>
-        @clonedModel = _.extend({},model) #changed from _.clone(model, true) eliminates lodash dep (so you can use underscore)
+        @clonedModel = _.clone(model,true) #changed from _.clone(model, true) eliminates lodash dep (so you can use underscore)
         @setMyScope 'all', model, @model
 
       renderGMarker: (doDraw = true, validCb) ->

src/coffee/directives/api/models/child/window-child-model.coffee

@@ -199,7 +199,7 @@ angular.module('uiGmapgoogle-maps.directives.api.models.child')
             @scope.$destroy()
 
         updateModel: (model) =>
-          @clonedModel = _.extend({},model)
+          @clonedModel = _.clone(model,true)
           _.extend(@model, @clonedModel)
 
       WindowChildModel