Contribution documentation

I noticed a couple of small issues when viewing your contribution instructions. 

1. Your CONTRIBUTING.md file seems to end mid sentence. 
2. In the Contributing section of the README.md file, the first instance of request as in pull request is misspelled.

I would have submitted a PR for 2, but I didn't know what exactly 1 was supposed to say, and this seemed to small to file 2 issues for.