fix(packaging): tsconfig was configured with the wrong module flag (#1167)

Author: hansl

src/lib/tsconfig.json

@@ -5,7 +5,7 @@
     "experimentalDecorators": true,
     "lib": ["es6", "es2015", "dom"],
     "mapRoot": "",
-    "module": "umd",
+    "module": "es2015",
     "moduleResolution": "node",
     "noEmitOnError": true,
     "noImplicitAny": true,