Direct link to the RailsInstaller download so students don't get sidetracked.
Add explanation of home directory.
Indent the home directory note with the rest of the list.
Update to secure rubygems source.
Space before code fence
Stray tildes
Stray tilde
Add missing 'is'
Revert "Direct link to the RailsInstaller download so students don't get sidetracked."

This reverts commit 50a9fa3403d16f192b342664396081364cd30c8b.