Fix this in harness and improve gulpfile defaults

src/harness/harness.ts

@@ -127,7 +127,7 @@ namespace Utils {
     export function memoize<T extends Function>(f: T): T {
         const cache: { [idx: string]: any } = {};
 
-        return <any>(function() {
+        return <any>(function(this: any) {
             const key = Array.prototype.join.call(arguments);
             const cachedResult = cache[key];
             if (cachedResult) {