Add new md file WORKFLOW

  - this .md contains aditional information to CONTRIBUTING.md,
  showing how to create a new branch, rebase with master, commit
  and push to remote, opening a pull request. In order to have a
  defined workflow with git branches, avoiding a master without a
  good history, I added this suggestion.
Add Workflow link to README.md
Merge pull request #58 from RocketBoard/ramon-add-new-md

Add new md