align gemfile for travis testing

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
update travis file to current test specs

* add puppet 3.6
* remove puppet 3.4
* ignore failing tests in puppet 2.7+3.0 for ruby 2.0+

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>