I prefer simple tactics to `match ... in ... return ...`
I prefer `exact _` to `typeclasses eauto`
few style fixes
Don't use "Set Implicit Arguments" in the core.
Add quick and vi2vo targets

It doesn't seem to help much at the moment, but maybe we'll grow some
very slow Qed'ed proofs and want to use this target.

c.f.
https://github.com/coq/coq/blob/trunk/doc/refman/AsyncProofs.tex#L98 for
documentation.

```bash
$ make clean
...
$ time make -j10
real    2m51.868s
user    4m7.179s
sys     8m45.765s

$ make clean
...
$ time make quick -j10

real    2m54.031s
user    4m15.360s
sys     8m52.969s

$ time make vi2vo J=10

real    0m21.458s
user    0m9.161s
sys     0m17.161s

```

This closes #471.
Merge pull request #469 from mikeshulman/implicit

Don't use "Set Implicit Arguments" in the core.
Merge pull request #465 from mikeshulman/prod

Some stylistic preferences in Prod.v
Merge pull request #459 from spitters/master

Using the standard (type class based) transitivity tactic for more contr...
Move ObjectClassifier and UniverseLevel out of types/
delete contrib/V.v (now it's in hit/)
also change the pointers in HoTT.v
remove notation `!`; use `const (center _)` or `const tt`
fix pointers to moved files
Merge pull request #482 from mikeshulman/const

remove notation `!`; use `const (center _)` or `const tt`
Merge pull request #480 from mikeshulman/move

Move ObjectClassifier and UniverseLevel out of types/
uniformize reflective subuniverses and modalities
truncation is a modality
Clean up Pushout.v a bit
join
open and closed modalities