Relax SHELL export checking
Relax SHELL export checking

So that the integration specs can be run locally when
$SHELL is not bash

craigcitro/travis-build,andyli/travis-build,JuliaCI/travis-build,kevmoo/travis-build,kevmoo/travis-build,JuliaCI/travis-build,andyli/travis-build,craigcitro/travis-build