Use the new beta build env on Travis

caching is only available on the new build env
added --jobs and --retry to bundler install as this installs gems faster
added --deployment back, it is best practice, especially when you have a Gemfile.lock
the new build env has more ram, more cpu, and better network stability
(docs coming soon)
Merge branch 'patch-1' of github.com:joshk/tdiary-core into joshk-patch-1
removed deployment option
Merge branch 'joshk-patch-1'