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

dzmitryv/puppetlabs-apache,gerhardsam/puppetlabs-apache,digitalmediacenter/puppetlabs-apache,samuelb/puppetlabs-apache,dzmitryv/puppetlabs-apache,svanhart/puppetlabs-apache,samuelb/puppetlabs-apache,gerhardsam/puppetlabs-apache,bmjen/puppetlabs-apache,yakatz/puppetlabs-apache,puppetlabs/puppetlabs-apache,FlatKey/puppetlabs-apache,puppetlabs/puppetlabs-apache,yakatz/puppetlabs-apache,buzzdeee/puppetlabs-apache,eputnam/puppetlabs-apache,digitalmediacenter/puppetlabs-apache,guegue/puppetlabs-apache,eputnam/puppetlabs-apache,guegue/puppetlabs-apache,buzzdeee/puppetlabs-apache,traylenator/puppetlabs-apache,bmjen/puppetlabs-apache,traylenator/puppetlabs-apache,svanhart/puppetlabs-apache,FlatKey/puppetlabs-apache