Duplicates of CONTRIBUTING and LICENSE files.

[pelesh]

It seems that the original contributing instructions are still at the same location as they were before making this a duplicate. We need to decide where we will kep this documentation and have a single place to keep it.

Similar to coding style guidelines, the license file is duplicate (actually a triplicate) with copies in LICENSE.md file in the ReSolve root directory and markdown and rest versions in docs/sphinx directory. We need a single place where we will keep this document.

Originally posted by @pelesh in #44 (comment)