Improved `--help` output

I did a series of things to make the `--help` output a little more human-friendly, and this is the end result.  

(If you don’t like all the changes I made, I broke them up into separate branches; so just let me know, and I’ll send pull requests for the changes in smaller bits.  Otherwise, if you like them, they’re all together here for easier merging. :smile:)