Added button that allows people get built application in their devices from browser

Hey,

I've added 'Install app' button into your README file. Anyone could try your sample application right in browser. Look how it's working!

To learn more, please look at: http://macbuildserver.com/github/opensource/
Merge pull request #17 from macbuildserver/patch-1

Added button that allows people get built demo application in their devices from browser