Disable browser testing on Travis CI

Our Travis CI system has always been unreliable when it came to running our browser tests. It's gotten to the point that it's simply unacceptable. I no longer have faith in the notifications from Travis.

It also looks like Travis is using an old version of the sauce connect platform in their official plugin, which we are using.

This removes the testing from our CI process, pending review of how to make this work better. To be honest, I am eyeing snap-ci (which would be as free as travis, and is more featureful) as a replacement.