Use <sup> for exponentiation

[martinthomson]

This renders much better in HTML and the text format does not suffer for
it.

Conversion process was almost entirely mechanical:

sed -i -e 's/\^\([0-9][0-9]*\(\|\.[0-9][0-9]*\)\)/<sup>\1<\/sup>/g' draft-*.md
sed -i -e 's/<\/sup> - /<\/sup>-/' draft-*.md

Cleanup used emacs because I know that wraps reliably.

emacs $(git status --porcelain | cut -d ' ' -f 3 -)

With the macro sequence:

C-X ( C-s '<sup ENTER M-q C-x )

Then for each file it was basically just:

C-u 99 C-x e C-x C-s

Though I had to manually wrap the changelogs because emacs got greedy.

[janaiyengar]

Can you also change this in the recovery draft? This does make it slightly odd that the HTML version will still say that "^ is exponentiation", but that's not incorrect, just redundant.

[janaiyengar]

Since recovery is only in the pseudocode, LGTM.