Update Travis to use Ruby 2.5.3 and Packer 1.3.2
Update Travis to use Ruby 2.5.3 and Packer 1.3.2

Update to the latest versions in Travis

Signed-off-by: Tim Smith <764ef62106582a09ed09dfa0b6bff7c05fd7d1e4@chef.io>

devopxteam/bento,norcams/bento,chef/bento,chef/bento,chef/bento,devopxteam/bento,norcams/bento,devopxteam/bento,norcams/bento,devopxteam/bento