[Tests] Run shellcheck on nvm-exec in Travis CI
[Tests] Run shellcheck on nvm-exec in Travis CI

ljharb/nvm,edwmurph/nvm,edwmurph/nvm,evocateur/nvm,PeterDaveHelloKitchen/nvm,ljharb/nvm,PeterDaveHello/nvm,evocateur/nvm,PeterDaveHello/nvm,creationix/nvm,PeterDaveHelloKitchen/nvm,creationix/nvm