Some minor changes based on how the SF workshop ran for everyone to review

We probably want to back off the 1.9.3 minimum on Git. I'm on 1.7.12.4 and that's absolutely fine for the workshop. I don't know what is installed by default on 10.6.8? Saying 1.9.3 was the minimum caused a fair bit of confusion and extra work at the InstallFest.

Most of the changes in the Leiningen section should be non-controversial as they are just intended to be clarifications that improve the accuracy of the process.

The truth vs truthy change came out of some confusion over true vs truthy so I think that's probably a good change, esp. since Clojurians tend to say "truthy" and "falsey" when talking about this.
> I think `zsh` is the Mac default?

`bash` is, actually.