emphasize that path induction gives a specified function, close #338
A different fix for variable shadowing in Lemma 11.2.2.

Conflicts with #392.
add b002a64 to errata
well-formedness of a context is not just variable containment, close #394
add 76db618 to errata
fix proof of 11.2.4, close #372
add 179b359 to errata
add 4ef49f7 to errata
chaining equalities concatenates paths
add ac9b226 and 18642ca to errata
Merge pull request #400 from mikeshulman/chainingequalitiesagain

chaining equalities concatenates paths
Merge pull request #398 from mikeshulman/theorem11.2.4

fix proof of 11.2.4, close #372
Merge pull request #397 from mikeshulman/wfctx

well-formedness of a context is not just variable containment, close #394
Merge branch 'lemma11.2.2'

Conflicts:
	errata.tex
Merge branch 'pathinduction'

Conflicts:
	errata.tex