Some letter B
Merge branch 'master' of github.com:HoTT/book

Conflicts:
	equivalences.tex
	hits.tex
	homotopy.tex
	preliminaries.tex
	reals.tex
Index letters Z and Y. But ...

why doesn't "ZF" and "Zermelo--Fraenkel set theory" appear in the index?!
index letters u v w x y