Add blurb about what mix is and how it got installed, to the Elixir install doc.
Add verification of Mix's version
Note: During installfest, mix is all of the sudden used with no information. This is just to inform users how it got there, what it is, and how to verify its version.
Things Done
Note: During installfest, mix is all of the sudden used with no information. This is just to inform users how it got there, what it is, and how to verify its version.