more detail on code review process

[pdpinch]

swiped from HipChat:

• sqaush all your commits and rename the comment to the PR title. The PR title should be in the past tense by the way so we can easily reuse it for release notes
• make sure all tests pass, you can see this with the green check mark from travis
• then it's up to you to merge the PR by clicking the merge button
• then delete the branch by clicking the button at the bottom of the PR