Rely on the `jar` command instead of `unzip` to unpack the cli.jar

Fixes #180
Fixes #135
Upgrade Vagrant dependency to hope Travis does the right thing
Ensure we're using bundle exec for travis
Exclude the Vagrant plugins group when we install in travis too
Force a version of bundler that Vagrant works with
Merge pull request #183 from rtyler/issues/135-unzip-not-available

Rely on the `jar` command instead of `unzip` to unpack the cli.jar