message: master -> main in Contributing.md
diff: @@ -23,7 +23,7 @@ reported the issue. Please try to include as much information as you can. Detail
  ## Contributing via Pull Requests
  Contributions via pull requests are much appreciated. Before sending us a pull request, please ensure that:
  -1. You are working against the latest source on the *master* branch.
  +1. You are working against the latest source on the *main* branch.
  2. You check existing open, and recently merged, pull requests to make sure someone else hasn't addressed the problem already.
  3. You open an issue to discuss any significant work - we would hate for your time to be wasted.
  