Clarifying how to use the editor

[tbooth]

from @tkphd

Two editors are mentioned here, but no editor is invoked in the lesson material. Throughout, when showing changes to a file, preface it with the command the instructor should use to launch the editor. Provide installation instructions or suggest a framework (like gitforwindows) that provides an editor. "Setup" is meant to be run by the learner hours or days ahead of the workshop. Any alias they set will be lost by the time they need it. Recommend editing ~/.nanorc to set appropriate flags instead, or editing ~/.bashrc to retain the alias, and revisiting this at the beginning of the lesson to make sure everyone has a consistent editing environment.