Add license

[xiongchiamiov]

Adding an explicit license to your code is good so that other people can safely modify it and use bits and pieces for other things. Since this is an example, you presumably are particularly interested in this use-case.

There is an unfortunate chain of non-licensing from iFixit/pulldash#13 to stefanbuck/sails-social-auth-example#1 to this project; until you retroactively license the code they've built upon, they cannot relicense their work (and they're also violating the Berne Convention rules of copyright).

If you find the maze of licensing options to be a little much, please let me know and I'll provide a short list with some explanations.