Add beaker tests

This PR adds basic beaker test coverage, updates the Rakefile and .travis.yml to use puppet-syntax/tasks/puppet-syntax for linting instead of the ones currently built into the Rakefile, and removes the ruby-bundler package from ruby::dev in order to make Debian/Ubuntu pass beaker tests.

I'd be glad to separate these into a few different pull requests if there's disagreement on individual changes. The reason for my interest in this is that adding ruby-bundler to ruby::dev breaks it on Debian/Ubuntu, and so the ploperations/puppet-puppet module breaks when using the current master version of ruby::dev. Beaker integration tests should help avoid future breakage.