Don't let me commit to blog.servo.org

[paulrouget]

I just commited a change to blog.servo.org by mistake: 3add526

Github allows me to edit a markdown file, and create PR, but I clicked on "Commit" instead of "Create a PR".

Maybe we should add something to prevent accidental commits.

[wafflespeanut]

It doesn't have a master branch, since we're using gh-pages. @larsbergstrom Does Github allow us to lock that branch?

[jdm]

We actually encourage people to commit directly to the blog when making small changes.