docs improvements based on Camila's remarks

[lucasgautheron]

• [x] explicit how to check which version of python pip refers to
• [ ] what to do in case of package version clash
• [ ] how to install brew if not installed. Camila: Marvin avait fait un truc pas mal pour ça (dans le cadre d'un système de diarization)
• [x] Instructions to make sure everything is properly installed
• [x] private key -> public key typo in ssh/github
• [x] remind that lgautheron should be replaced with your username
• [x] replace ssh instructions for oberon with flores instead of frontal
• [x] datalad way typo (two 1. items in the list)
• [ ] explicit expected output all the time
• [ ] publishing data tutorial
  • [ ] osf datalad push issue fix
  • [x] embed cluster into remote.log
• [x] add link to create a GitHub issue in case someone needs help ?