Actually re-order the lessons

[reid-a]

The flexibility to re-order lessons has been introduced with the closure of #230, which is itself the successor of the venerable and ancient issue #9.

It remains to actually rename the files to introduce spaces in the numbering scheme, and to change the order.

[tkphd]

Renumbering was one of the earliest issues, but the current order seems correct, no? See my comment on #226.

[reid-a]

There is also the comment from @psteinb on issue #230, which proposed a different ordering, moving the "Resonsibility" part up several notches. I am unclear on whether this was a straw-man to illustrate re-ordering, or whether it was a serious re-ordering proposal, and, related, whether there are other proposed orderings out there that merit discussion.

If there are, then this is the venue for that disucssion!