Getting started edits

These two proposed edits are based upon feedback I've gotten from participants:

- I've often been asked what `-T` means when generating the Rails app
- I've often been asked what `g` meant in the rails command and why `body` needs a data type but `title` does not.
Yeah, in my time going to InstallFest I've never seen anyone start from scratch and make it past the second section, but point taken, so I'll make a change so it says "We won't be specifically covering testing just now, ..."