Page container: the load method now correctly returns a promise

The API docs for version 1.4.0 state that the load method of the pagecontainer
widget returns a promise. This commit adds this behaviour to the widget to
comply with the docs.

Closes gh-6901
Fixes gh-6900

Author: marcuskrahl

js/widgets/pagecontainer.js

@@ -637,7 +637,7 @@ define( [
 				$.mobile.path.isEmbeddedPage(fileUrl) &&
 				!$.mobile.path.isFirstPageUrl(fileUrl) ) {
 				deferred.reject( absUrl, settings );
-				return;
+				return deferred.promise();
 			}
 
 			// Reset base to the default document base
@@ -658,7 +658,7 @@ define( [
 					this._getBase().set(url);
 				}
 
-				return;
+				return deferred.promise();
 			}
 
 			triggerData = {
@@ -675,7 +675,7 @@ define( [
 			// If the default behavior is prevented, stop here!
 			if ( pblEvent.deprecatedEvent.isDefaultPrevented() ||
 				pblEvent.event.isDefaultPrevented() ) {
-				return;
+				return deferred.promise();
 			}
 
 			if ( settings.showLoadMsg ) {
@@ -691,7 +691,7 @@ define( [
 			if ( !( $.mobile.allowCrossDomainPages ||
 				$.mobile.path.isSameDomain($.mobile.path.documentUrl, absUrl ) ) ) {
 				deferred.reject( absUrl, settings );
-				return;
+				return deferred.promise();
 			}
 
 			// Load the new content.
@@ -704,6 +704,8 @@ define( [
 				success: this._loadSuccess( absUrl, triggerData, settings, deferred ),
 				error: this._loadError( absUrl, triggerData, settings, deferred )
 			});
+			
+			return deferred.promise();
 		},
 
 		_loadError: function( absUrl, triggerData, settings, deferred ) {