Merge pull request #312 from rpglover64/issue312

Missing parenthesis in Ch. 1 exercises (p. 54)
Merge pull request #308 from rpglover64/master

Fix spacing on page 50, section 1.12.2
fixing typo in preliminaries
fixing typo in preliminaries
the paradoxes of self-reference are not specific to set theory
a remark about alternative universe handling
Merge pull request #316 from mikeshulman/selfreference

the paradoxes of self-reference are not specific to set theory
remove "merely" and mention "directedness" #317
clarify and index Fin(n), fix #294 and see #297
another example of a polymorphic function, close #297
fix #305
more comments on universes, fix #296
Merge pull request #319 from mikeshulman/fin

finite types and polymorphic functions
Merge pull request #320 from mikeshulman/fiberseq

fix #305
Merge pull request #317 from mikeshulman/universes

a remark about alternative universe handling
explain recursion on product types better, fix #311
remove tilde, fix #309
Merge pull request #321 from mikeshulman/products

explain recursion on product types better, fix #311