fix: add debounce to computeUrl to remove angular2 multiple api error

fix #67

Author: MrChoclate

Diff for: google-maps-api.html

@@ -103,11 +103,20 @@
 
       /** @private */
       libraryUrl: {
-        type: String,
-        computed: '_computeUrl(mapsUrl, version, apiKey, clientId, language, signedIn)'
+        type: String
       }
     },
 
+    observers: [
+      '_debounceComputeUrl(mapsUrl, version, apiKey, clientId, language, signedIn)'
+    ],
+
+    _debounceComputeUrl: function(mapsUrl, version, apiKey, clientId, language, signedIn) {
+      this.debounce('_computeUrl', function () {
+        this.libraryUrl = this._computeUrl(mapsUrl, version, apiKey, clientId, language, signedIn);
+      }, 0);
+    },
+
     _computeUrl: function(mapsUrl, version, apiKey, clientId, language, signedIn) {
       var url = mapsUrl + '&v=' + version;