Tweaked the README to be a bit more friendly and detailed

I thought the README could use some love, so I added some details about licensing and also detailed out procedures for downloading and building the project.

In addition I added a bit to the "What do you get" paragraph and tried to tighten it all up some.
Or Terminal.app or cmd.exe... I think we can assume anyone who is on GitHub and wants to clone our project knows what shell they would need to open to run git clone.