Create PULL_REQUEST_TEMPLATE.md

Created by: avullo

Trying to activate PR templates using a different route. From the docs: "If your current branch is master, you should choose to create a new branch for your commit and then create a pull request."

Created by: coveralls

Coverage remained the same at 81.995% when pulling ead35879 on avullo-patch-1 into feadb2b6 on master.