[Oops.] octotherp -> octothorp

[SethPoulsen]

Please verify that the error is present in the most recent revision before reporting.

Chapter number or note title: 2.5

Page number: 80

Error description: in the footnote, I believe "#octotherps4lyfe" should be "#octothorps4lyfe" (see https://en.wiktionary.org/wiki/octothorpe#English)

Suggested fix (if any): [fix]