Update CONTRIBUTING.md

[joeyklee]

Just leaving an issue here to make a note to update the CONTRIBUTING.md doc.

I made a video (resolution issues on youtube, will add a new one soon) about how to handle pull requests and updating the website if you're on the core Dev team and have access to merging changes etc: https://www.youtube.com/watch?v=dsUvqqhKmys&feature=youtu.be