minor fadeIn & grunt/minification

I made a minor change to make fadeIn more consistant (same look as fadeOut) and added Grunt, npm, and minification support.  It's an extra file to track version, but it might be worth it.  I'd be happy to write a grunt task that updates source & simpleModal.jquery.json with in package.json, so you only have to edit one file (package.json) and do a `grunt` to update minified file & version info.