Friendlier `--dev-mode` error message, new `help` command

![screen shot 2014-10-17 at 7 46 39 am](https://cloud.githubusercontent.com/assets/163977/4678263/574fab74-55f3-11e4-9630-4f6169e9d584.png)

so, we can make it the way it was:
"print usage on unknown commands along with unknown command error, and have the word help look like an error"

or we can have it like now:
"behaves like before, and doesn't tell you typing 'help' was an error"

I like the latter one better.