travis: ruby 2.5.5 and 2.6.2
travis: ruby 2.5.5 and 2.6.2

ramiroaraujo/image_optim,mihailim/image_optim,toy/image_optim,toy/image_optim,ramiroaraujo/image_optim,toy/image_optim,mihailim/image_optim,mihailim/image_optim,ramiroaraujo/image_optim