Fix puppet-lint and dpl gem

[bastelfreak]

git log messages:

commit 4c58c736e7f71baa6e6392b16ce800a697804a57
Author: Tim Meusel <tim@bastelfreak.de>
Date:   Fri Aug 19 11:02:40 2016 +0200

    pin puppet-lint to 2.0.0

    2.0.1 got released a few hours ago, the puppetlint-variablecase plugin
    isn't compatible with that:
    https://github.com/fiddyspence/puppetlint-variablecase/pull/6

    This workaround is tested in multiple releases, for example minecraft
    and mumble.

commit 9d3419624ba62e54b58881c100776fa5b8ef2d8d
Author: Tim Meusel <tim@bastelfreak.de>
Date:   Fri Aug 19 10:59:21 2016 +0200

    get dpl from specific branch

    During a release, travis installs the dpl gem. The latest released
    version is broken, the travis devs provided us a fix which is available
    in a certain branch: https://github.com/travis-ci/dpl/issues/487
    This fix is tested in several modules, fox example zabbix, gluster,
    minecraft

[roidelapluie]

Thanks!