fix reference in proof of 4.7.6, close #356.

I had to be careful not to alter the numbering of anything else on
this one, so whoever merges it should check that I didn't mess up.
Merge branch 'master' into sumoverpaths
add 3d119cf to errata
fix proof of 4.8.3, close #359
add d50b90e to errata
fix types in 8.6.11 and 8.6.12, close #391
add d5584c6 to errata
more on subscripts and implicit arguments, see #333
Remark on implicit dependencies, see #333
add 0ad2aba and 37b78ef to errata
fix typo
Update formal.tex

compared notation for judgmental equality with that in the intro
Update formal.tex
Update preliminaries.tex

changed notation for judge eq to agree with appendix
typo in 7.1.4, close #407
add b672a4d to errata
Merge pull request #405 from awodey/master

judgmental equality in Ch. 1
add b29ea2f to errata
Merge pull request #409 from mikeshulman/theorem7.1.4

typo in 7.1.4, close #407
Merge pull request #396 from mikeshulman/eq8.6.11

fix types in 8.6.11 and 8.6.12, close #391