cleaned up readme and license

I cleaned up the readme a bit. I shrunk the opening statement to one sentence, I hope you like it. I think it conveys the right message. I added an installation section to help out first-timers. And I reworked the "introduction" section (renamed "usage") a little so that the narrative wasn't stuffed into code comments/blocks.

I see a lot of projects with a LICENSE file without an extension. Dunno why, seems like an OSS convention. I added the date/name to this one from the Google Code site.