Update typescript version used in plunkers to 1.6.2

The [plunker template](http://plnkr.co/edit/tpl:AvJOMERrnz94ekVua0u5) uses TS version 1.6.0-beta [pulled from code.angularjs.org](https://github.com/angular/code.angularjs.org/tree/master/tools). This version is buggy.

Can we get it upgrade to 1.6.2 please?

Related to https://github.com/angular/angular/issues/4585#issuecomment-147103749
