Add 'Contributing' section to README.md.

Testing code contribution workflow.
<a href='#crh-start'></a><a href='#crh-data-%7B%22processed%22%3A%20%5B%22https%3A//github.com/gilt/gilt-swig/pull/1%23issuecomment-62791800%22%2C%20%22https%3A//github.com/gilt/gilt-swig/commit/00863b8937ac5c0b8442055174c6f7ebfed50129%23commitcomment-8545543%22%2C%20%22https%3A//github.com/gilt/gilt-swig/commit/00863b8937ac5c0b8442055174c6f7ebfed50129%23commitcomment-8545547%22%2C%20%22https%3A//github.com/gilt/gilt-swig/pull/1%23issuecomment-62792149%22%5D%2C%20%22comments%22%3A%20%7B%22General%20Comment%22%3A%20%7B%22html_url%22%3A%20%22https%3A//github.com/gilt/gilt-swig/pull/1%23issuecomment-62791800%22%2C%20%22comments%22%3A%20%5B%7B%22body%22%3A%20%22testing%20a%20new%20comment.%20seeing%20if%20crh%20triggers%22%2C%20%22created_at%22%3A%20%222014-11-12T20%3A56%3A14Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/76371%3Fv%3D3%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/shellscape%22%7D%7D%2C%20%7B%22body%22%3A%20%22%3Apoop%3A%20%22%2C%20%22created_at%22%3A%20%222014-11-12T20%3A58%3A15Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/939776%3Fv%3D3%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/cblage%22%7D%7D%5D%2C%20%22title%22%3A%20%22General%20Comment%22%7D%2C%20%22Commit%2000863b8937ac5c0b8442055174c6f7ebfed50129%20README.md%206%20141%22%3A%20%7B%22html_url%22%3A%20%22https%3A//github.com/gilt/gilt-swig/commit/00863b8937ac5c0b8442055174c6f7ebfed50129%23commitcomment-8545543%22%2C%20%22comments%22%3A%20%5B%7B%22body%22%3A%20%22oh%20man%2C%20this%20line%20is%20the%20worst%22%2C%20%22created_at%22%3A%20%222014-11-12T20%3A56%3A58Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/76371%3Fv%3D3%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/shellscape%22%7D%7D%5D%2C%20%22title%22%3A%20%22File%3A%20README.md%3AL141%20%2800863b8%29%22%7D%2C%20%22Commit%2000863b8937ac5c0b8442055174c6f7ebfed50129%22%3A%20%7B%22html_url%22%3A%20%22https%3A//github.com/gilt/gilt-swig/commit/00863b8937ac5c0b8442055174c6f7ebfed50129%23commitcomment-8545547%22%2C%20%22comments%22%3A%20%5B%7B%22body%22%3A%20%22worst.%20pull%20request.%20evar%21%22%2C%20%22created_at%22%3A%20%222014-11-12T20%3A57%3A12Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/76371%3Fv%3D3%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/shellscape%22%7D%7D%5D%2C%20%22title%22%3A%20%22Commit%2000863b8%20comments%22%7D%7D%7D'></a>
<a href='https://www.codereviewhub.com/'><img src='http://www.codereviewhub.com/site/github-bar.png' height=40></a>
- [x] <a href='#crh-comment-General Comment'></a> <img src='http://www.codereviewhub.com/site/github-remaining.png' height=16 width=60>&nbsp;<b><a href='https://github.com/gilt/gilt-swig/pull/1#issuecomment-62791800'>General Comment</a></b>
- <a href='https://github.com/shellscape'><img border=0 src='https://avatars.githubusercontent.com/u/76371?v=3' height=16 width=16'></a> testing a new comment. seeing if crh triggers
- <a href='https://github.com/cblage'><img border=0 src='https://avatars.githubusercontent.com/u/939776?v=3' height=16 width=16'></a> :poop:
- [x] <a href='#crh-comment-Commit 00863b8937ac5c0b8442055174c6f7ebfed50129 README.md 6 141'></a> <img src='http://www.codereviewhub.com/site/github-remaining.png' height=16 width=60>&nbsp;<b><a href='https://github.com/gilt/gilt-swig/commit/00863b8937ac5c0b8442055174c6f7ebfed50129#commitcomment-8545543'>File: README.md:L141 (00863b8)</a></b>
- <a href='https://github.com/shellscape'><img border=0 src='https://avatars.githubusercontent.com/u/76371?v=3' height=16 width=16'></a> oh man, this line is the worst
- [ ] <a href='#crh-comment-Commit 00863b8937ac5c0b8442055174c6f7ebfed50129'></a> <img src='http://www.codereviewhub.com/site/github-remaining.png' height=16 width=60>&nbsp;<b><a href='https://github.com/gilt/gilt-swig/commit/00863b8937ac5c0b8442055174c6f7ebfed50129#commitcomment-8545547'>Commit 00863b8 comments</a></b>
- <a href='https://github.com/shellscape'><img border=0 src='https://avatars.githubusercontent.com/u/76371?v=3' height=16 width=16'></a> worst. pull request. evar!


<a href='https://www.codereviewhub.com/gilt/gilt-swig/pull/1?mark_as_completed=1'><img src='http://www.codereviewhub.com/site/github-mark-as-completed.png' height=26></a>&nbsp;<a href='https://www.codereviewhub.com/gilt/gilt-swig/pull/1?approve=1'><img src='http://www.codereviewhub.com/site/github-approve.png' height=26></a>&nbsp;<a href='https://github.com/gilt/gilt-swig/pull/1'><img src='http://www.codereviewhub.com/site/github-refresh.png' height=26></a>
<a href='#crh-end'></a>