add npmignore, closes #512

.npmignore

+2/
+api/
+assets/
+bower_components/
+custom/
+default/
+global/
+help/
+tests/
+_config.yml
+.bowerrc
+.gitignore
+.travis.yml
+bower.json
+CNAME
+composer.json
+favicon.ico
+Gemfile
+Gruntfile.js
+index.html
+*/index.html