Condense 2 tutorials into 1

[jsms90]

The current version of the FAC curriculum has only one slot for learning git & github. By week 2, students are now expected to know all of the content in this workshop.

So it would be good to restructure this tutorial slightly and remove these references at the beginning:

The introduction to Git is aimed at the first week of the full time Founders & Coders course

Git for Collaboration is aimed at the second week students of the course

If we're condensing it, we will also need to:

• move the "GitHub flow" section to the top, before the workshop begins.
• remove:

Before we start make sure you have a terminal open located at the local copy of this repo. The same one that was used for the first tutorial is essential.