fix(map-loader): change includeScript to place maps api script tag to head element instead of body

Placing the script tag in document body causes the Google Maps API to be included multiple times
when document is stored using the History API and then later retrieved (e.g. when using
Turbolinks.js). Placing the script tag inside head element solves this problem, ensuring the Google
Maps API is loaded only once.

Author: lkol

dist/angular-google-maps-street-view.js

@@ -1,4 +1,4 @@
-/*! angular-google-maps 2.3.3 2016-06-03
+/*! angular-google-maps 2.3.3 2016-07-16
  *  AngularJS directives for Google Maps
  *  git: https://github.com/angular-ui/angular-google-maps.git
  */
@@ -109,7 +109,7 @@ return UUID;
         script.id = scriptId = "ui_gmap_map_load_" + (uuid.generate());
         script.type = 'text/javascript';
         script.src = getScriptUrl(options) + query;
-        return document.body.appendChild(script);
+        return document.head.appendChild(script);
       };
       isGoogleMapsLoaded = function() {
         return angular.isDefined(window.google) && angular.isDefined(window.google.maps);

dist/angular-google-maps-street-view.min.js

@@ -1,4 +1,4 @@
-/*! angular-google-maps 2.3.3 2016-06-03
+/*! angular-google-maps 2.3.3 2016-07-16
  *  AngularJS directives for Google Maps
  *  git: https://github.com/angular-ui/angular-google-maps.git
  */
@@ -96,7 +96,7 @@ Nicholas McCready - https://twitter.com/nmccready
         script.id = scriptId = "ui_gmap_map_load_" + (uuid.generate());
         script.type = 'text/javascript';
         script.src = getScriptUrl(options) + query;
-        return document.body.appendChild(script);
+        return document.head.appendChild(script);
       };
       isGoogleMapsLoaded = function() {
         return angular.isDefined(window.google) && angular.isDefined(window.google.maps);