Added extras and examples-js folders to nam package

Bower package already contains examples-js folder, and extras also has
some very good helpers, so it will be good to have them in npm package
as well

.npmignore

@@ -1,5 +1,7 @@
-examples/
-src/
+examples/*
+!examples/js/
+src/*
+!src/extras/
 test/
 utils/
 docs/