Don't refer to grandparent commit as second parent

The term "second parent" has a specific meaning in git that is distinct
from a grandparent, so avoid referring to a grandparent (~2) as a second
parent (^2).
Merge pull request #78 from aschrab/grandparent

Don't refer to grandparent commit as second parent
Typos, clarifications, and a missing hint for the ramp up levels.
Merge pull request #79 from donkirkby/ramp-up-typos

Typos, clarifications, and a missing hint for the ramp up levels.
Rebuild for Pull #79 and Pull #78
Better flip logic, visuals improvement, and also advanced level section
featuring Aaron's modifier tutorial

Merge pull request #80 from aschrab/multiple_parents