Branches have different versions of the code

[benthayer]

After talking to someone, I realized that it wasn't clear how commits saved different versions of the code or that by checking out a branch, you were checking out a different version of the code.

It would be worth digging into the different conceptions held, but one level we could do could have them check out the different versions of the code on the different branches and inspect it to see that it's different.

This might call for having users provide manual input to verify they have read the contents of the files and have seen the differences.

[benthayer]

Closing in favor of #238