.travis.yml: add sudo: required
.travis.yml: add sudo: required

Avoid Travis CI error for zsh on linux:

   $ ./test/support/travisci_deps.sh
   This job is running on container-based infrastructure, which does not
   allow use of 'sudo', setuid, and setgid executables.  If you require
   sudo, add 'sudo: required' to your .travis.yml

ndbroadbent/scm_breeze,ndbroadbent/scm_breeze,scmbreeze/scm_breeze,scmbreeze/scm_breeze