fix(ngFor): give more instructive error when binding to non-iterable

Before, you'd get an error like:

```
EXCEPTION: Cannot find a differ supporting object ‘[object Object]’ in [users in UsersCmp@2:14]
```

Now, you get:

```
EXCEPTION: Cannot find a differ supporting object ‘[object Object]’ of type 'Object'. Did you mean to bind ngFor to an Array? in [users in UsersCmp@2:14]
```

modules/angular2/src/facade/lang.ts

@@ -62,7 +62,10 @@ export interface Type extends Function {}
 export interface ConcreteType extends Type { new (...args): any; }
 
 export function getTypeNameForDebugging(type: Type): string {
-  return type['name'];
+  if (type['name']) {
+    return type['name'];
+  }
+  return typeof type;
 }