Better acknowledgements of third-party code

[arjunguha]

I now remember that we have third-party code copied into this repository, for example:

https://github.com/umass-compsci220/Ocelot/pull/82/files#diff-2887097bfa77f555fb01358ac01e664dL3

We should do a better job of accumulating licenses and displaying them. Perhaps it can all go in the LICENSE file and the website can just have a link to the LICENSE on GitHub.