Revert "Attempt to fix by not using sudo"

This reverts commit 2a09be467657d76db5c463ebf1985fc5852e2950.
Revert "Use sudo: false in .travis.yml"

Until someone wants to build zsh binaries to update the build process,
we have to have sudo access to apt-get install things.

This reverts commit f66cd2840596ec5aa2b9302b569fc08203fce8a3.