links HoTTBook, Ch. 2.10-15 -> library
Merge pull request #287 from JasonGross/functor-category-op

Define the functor (C -> D)^op -> (C^op -> D^op)
Merge pull request #286 from marcbezem/master

Done with references HoTTBook, Ch.2 -> library (second try)
Fix @marcbezem's "double entry" and put in more instructions on how to use HoTTBook.v
Merge pull request #288 from andrejbauer/master

Fix @marcbezem's "double entry" 

I am pulling this in because #286 introduced a problem that this pull request fixes.
fix typo in HoTTBook.v: config -> contrib
Use maintainer mode in configure

This will automatically rebuild Makefile and configure if needed,
preventing problems like the missing targets in
https://github.com/HoTT/HoTT/pull/286#issuecomment-30749614.  This means
that we now depend on having autobuild around to run ./configure and
make, though I think that systems without them will simply get warnings,
and not errors.
Merge pull request #289 from JasonGross/fix-book-typo

fix typo in HoTTBook.v: config -> contrib
Remove support for ssreflect

The ssreflect support has been inactive for a long time now. It would
take some effort to make it work, and it is unlikely this will happen.
So I am ripping it out. If in the future anyone wants to put it back
in, they can have a look at the history and go from there.
Remove further traces of ssreflect.
Add some more synonyms of [apD10_path_forall] for rewriting
Merge pull request #293 from JasonGross/ap10-path-forall

Add some more synonyms of [apD10_path_forall] for rewriting
Deopacify a bit in Functor/Pointwise/Properties

This is necessary to construct pointwise adjunctions.
Update a reference in a comment that was renamed

Closes #297.
Split off HoTTBookExercises.v from HoTTBook.v.

Since exercise formalizations tend to be a lot wordier than mere
backreferences to theorems in the library (as discussed in PR #302),
this patch splits HoTTBook.v into a separate exercises file, which
contains formalizations for the exercises in the HoTT book.  etc/Book.v
now takes a new flag, '--exercises', which instructs it to extract out
only exercises from the book; its default setting now no longer inserts
markers for exercises.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>
Merge pull request #303 from ezyang/split-exercises

Split off HoTTBookExercises.v from HoTTBook.v.
Add HoTTBookExercises.v to Makefile_targets.mk

This was forgotten in #303.
Merge pull request #292 from andrejbauer/master

Remove ssreflect "support" which isn't working anyhow.
Merge pull request #290 from JasonGross/enable-maintainer-mode

Use maintainer mode in configure
Move developer note to non-rendered section.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>