docs(npm-packages): typo ES6 = ES2015

closes #1263

Author: mdhooge

public/docs/ts/latest/guide/npm-packages.jade

@@ -103,7 +103,7 @@ a(id="polyfills")
   :marked
     See "[Why peerDependencies?](#why-peer-dependencies)" below for background on this requirement.
 :marked
-  ***es6-shim*** - monkey patches the global context (window) with essential features of ES2016 (ES6).
+  ***es6-shim*** - monkey patches the global context (window) with essential features of ES2015 (ES6).
    Developers may substitute an alternative polyfill that provides the same core APIs. 
    This dependency should go away once these APIs are implemented by all supported ever-green browsers.