UPDATED: highlight more effectively, the purpose of the README

[chalmerlowe]

We need to find a place to elaborate for the student on the typical purpose of README.md files.

In that file, we need to add a sentence OR three on why projects have README.md files and how projects displayed on github benefit (i.e. github auto displays the file as the project summary on the main page of any given project).

This pages seems like a good candidate:
https://github.com/chalmerlowe/intro_to_sprinting/blob/dd81d26f9f5a029f7207df7654d9643228f5e2e0/class_materials/github_concepts.md