revise .travis.yml to prevent intermittent time-outs during testing
revise .travis.yml to prevent intermittent time-outs during testing

Revised 'sudo rm -rf ...' line by:
 - prefixing 'travis_wait' to double allowable time before time-out
 - replaced deprecated '/opt/homebrew-cask/Caskroom' with '/usr/local/Caskroom'

mikemcquaid/strap,mikemcquaid/strap,mikemcquaid/strap