Update .travis.yml
Update .travis.yml

This commit makes the following changes to the test matrix:

- Runs tests on ruby 2.1.5 instead of 2.0.0
- Runs tests on ruby 1.8.7 with puppet 3.x
- Adds an environment to run on an intermediate 3.x puppet version
  instead of latest (specifically 3.4.x)
- Adds an environment to run with the future parser on latest puppet.
  This would affect the test runs for the validate and spec checks.
- Runs the tests on docker

BCLibCoop/puppetlabs-ntp,HelenCampbell/puppetlabs-ntp,dpash/puppetlabs-ntp,harniman/puppetlabs-ntp,nickchappell/puppetlabs-ntp,ocadotechnology/puppetlabs-ntp,harniman/puppetlabs-ntp,rdo-puppet-modules/puppetlabs-ntp,ocadotechnology/puppetlabs-ntp,redhat-cip/puppetlabs-ntp,DavidS/puppetlabs-ntp,nickchappell/puppetlabs-ntp,DSI-Ville-Noumea/puppetlabs-ntp,petems/puppetlabs-ntp,traylenator/puppetlabs-ntp,puppetlabs/puppetlabs-ntp,xaque208/puppetlabs-ntp,bw-y/puppetlabs-ntp,bmjen/puppetlabs-ntp,MelanieGault/puppetlabs-ntp,bw-y/puppetlabs-ntp,powertoaster/puppetlabs-ntp,DSI-Ville-Noumea/puppetlabs-ntp,plumgrid/puppetlabs-ntp,raphink/puppetlabs-ntp,redhat-cip/puppetlabs-ntp,mysteq/puppetlabs-ntp,rdo-puppet-modules/puppetlabs-ntp,fuel-infra/puppetlabs-ntp,tphoney/puppetlabs-ntp,raphink/puppetlabs-ntp,traylenator/puppetlabs-ntp,plumgrid/puppetlabs-ntp,powertoaster/puppetlabs-ntp,tphoney/puppetlabs-ntp,mysteq/puppetlabs-ntp,puppetnix/puppetlabs-ntp,xaque208/puppetlabs-ntp,petems/puppetlabs-ntp,dpash/puppetlabs-ntp,puppetnix/puppetlabs-ntp,BCLibCoop/puppetlabs-ntp,HelenCampbell/puppetlabs-ntp,MelanieGault/puppetlabs-ntp