fix(TypeScript): pin to TypeScript 2.0.x, fix errors with Error subcl…

…assing

Because the the last build was pinned to 2.x.x, it built with TypeScript 2.1.x, which had breaking changes but was not a major release.

This should fix that.

package.json

@@ -186,7 +186,7 @@
     "source-map-support": "^0.4.0",
     "tslib": "^1.0.0",
     "tslint": "^3.15.1",
-    "typescript": "^2.0.6",
+    "typescript": "~2.0.6",
     "typings": "^2.0.0",
     "validate-commit-msg": "^2.3.1",
     "watch": "^1.0.1",