Factor out the common parts of of the hoq* scripts

Also add hoqdep
Move hoq-config script to top-level

This way, we can copy it more easily.
Bundle coq

This will hopefully pave the way to make it easier to build coq for new
users.
Auto-init the bundled coq on autogen.sh
Call HoTT/coq configure on ./configure
WIP bundle coq
Fix symlinks
Add some more symlinks to fix anomalies
Update configure to make coq correctly
Only build the bundled coq with travis
Update INSTALL a bit

Now it talks about the bundled Coq.  The extended instructions might be
a bit out of order.
Fix the install target
Fix .gitmodules
Fix INSTALL.txt numbering
WIP Use coq
Generate the symlinks in configure again

I don't see any other way to permit the use of either the bundled coq,
or a system one; we might not have the version of OCaml used to compile
the system Coq.

This closes #201.
Test with bundled and global Coq on travis
Improve symlink code
Make the Makefile actually work with bundled coq

Before, it was looking for it to be already installed.
Change to the right directory for travis