Use version-specific branches

Instead of master, branches should be named to match the version of the code. Even though this is a sandbox project, 6.x-1.x is still useful since it shows the branch is for D6.

Also, we don't have changing default branches yet on drupal.org. So, you'll have to create a new branch, and then delete the content of master and replace it with a README mentioning the branch name. See step 5 at https://drupal.org/node/1127732.