Added an Automator application that can be called from the Calendar App

Messing with launchd plists seems to be difficult for some so I've
added a Mac Automator app. This can be called from within a recurring
Calendar event on Mac to automatically downlad the bing image and set
it as your desktop image. Blog post to follow.
Minor updates to readme
Merge branch 'master' of https://github.com/thejandroman/bing-wallpaper

Conflicts:
	README.md