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