Cherry-picking changes from #185

@zhujian0805 contributed some excellent cheatsheets in #185, but some
binary files seem to have gotten mixed into the commit as well. This
commit cherry-picks the cheatsheet file changes from that PR while
leaving behind the cruft.

Also performed minor editing on some of the cheatsheets.
Merge pull request #189 from chrisallenlane/dev

Cherry-picking changes from #185