Allow switching language using lang url param

Currently if a language is selected and i18n messages
are missing the i18n code will be displayed instead

js/app/Messages.js

@@ -3,4 +3,19 @@
 var Polyglot = require( 'node-polyglot' ),
 	i18n = require( '../i18n.json' );
 
-module.exports = new Polyglot( { phrases: i18n[ 'de' ] } );
+var getParam = function getUrlParameter(sParam) {
+	var sPageURL = decodeURIComponent(window.location.search.substring(1)),
+		sURLVariables = sPageURL.split('&'),
+		sParameterName,
+		i;
+
+	for (i = 0; i < sURLVariables.length; i++) {
+		sParameterName = sURLVariables[i].split('=');
+
+		if (sParameterName[0] === sParam) {
+			return sParameterName[1] === undefined ? true : sParameterName[1];
+		}
+	}
+};
+
+module.exports = new Polyglot( { phrases: i18n[ getParam('lang') ] } );