message: Updated contribution guide.
diff: @@ -4,9 +4,8 @@ Contributing
  Follow these general instructions if you wish to contribute a new descriptor
  implementation to DScribe:
  - 1. Contact the authors to get initial approval for your idea of a new
  - descriptor implementation. Preferably backed up by publications or other
  - results.
  + 1. Contact the authors to discuss your idea for a new descriptor
  + implementation.
  2. Read the code style guideline (below).
  3. Fork the repository and do all modifications within it.
  4. Implement the descriptor as a class within a new module in
  @@ -23,7 +22,7 @@ implementation to DScribe:
  running *dscribe/regtests/testrunner.py*.
  7. Create tutorial for the descriptor in *dscribe/docs/src/tutorials*.
  Follow the structure of the existing tutorials.
  - 8. Create a pull request in Gitlab.
  + 8. Create a pull request in GitHub.
  Code style guideline
  --------------------
  