Add LICENSE.md file

https://help.github.com/articles/open-source-licensing#how-can-i-go-back-through-my-public-repositories-and-give-them-licenses
Merge pull request #38 from cmlh/license

Add LICENSE.md file
correct naming within the command injection tutorial
Merge branch 'master' of github.com:OWASP/railsgoat
shifting tutorials