Fix theories/Functorish.v

I'm not sure whether or not the last line in that proof is needed in an
old version of HoTT/coq, but I'm pretty sure it's not needed in the
newest version.  Chaining it with the previous command and adding a
[try] permits it to be run only if necessary.
Improve the [symmetry] and [etransitivity] tactics

It seems that [apply] uses an inferior(?) unificiation engine.  That of
[refine] and [exact] (and even [eapply], in some cases) are better, in
my experience.
Add .travis.yml for a travis-ci

This file will, if Travis CI is enabled for the repo by going to
https://travis-ci.org/profile/, add an automated build to check pull
requests for compatibility with HoTT/coq stable.  It is simple to modify
it to use trunk instead, should we desire.  Pull requests will be marked
with a green circle if they build, a yellow circle while they are
building, or a red circle if they fail, approximately 15-30 minutes
after they are submitted.
Merge pull request #167 from JasonGross/travis-ci

Add .travis.yml for a travis-ci

Looks like a convenient service.
Merge pull request #166 from JasonGross/fix-symmetry

Improve the [symmetry] and [etransitivity] tactics
Merge pull request #164 from JasonGross/fix-functorish

Fix theories/Functorish.v
Point travis-ci at HoTT/coq trunk

Now that we've split off a 'stable' branch, I think it makes more sense
to test whether or not master builds with trunk, on the trunk branch.
We also still test against stable, but allow it to fail.
Merge pull request #169 from JasonGross/trunk-travis-ci

Point travis-ci at HoTT/coq trunk
Merge branch 'master' of https://github.com/HoTT/HoTT