working on inductive types
improve weird inductive types in 5.6 and exercises, close #615
added some index entries
Update basics.tex

fixed a typo in Chapter 2
Merge pull request #630 from xcycl/patch-1

fixed a typo in Chapter 2
Uncommented the inclusion of main.labels
Merge pull request #628 from mikeshulman/weird-inductive-types

Weird inductive types
Add labels to all exercises without them.

This way, we can hook them up with the HoTT repository.  Labels were
sometimes made by keyword-pulling, when I couldn't immediately think
of a good name for the exercise.  I don't care much what the labels
are, but I would like all the exercises to have labels.
Typo in exercise 7.8
unmarked errata for a533a6b
Merge pull request #633 from mikeshulman/ex7.8

Typo in exercise 7.8
Merge pull request #632 from JasonGross/label-exercises

Add labels to all exercises without them.
Mark Errata (auto)
Logical equivalence between torus and product of circles
6.4.2 isn't using funext, close #640
errata for ec1373a
remark 1+n=n+1 is not judgmental
clarify exercises 5.2 and 5.3, close #639
errata for bd29d77
close #638