switch to puppetlabs_spec_helper

Removes librarian-puppet since puppetlabs_spec_helper
can now handle installing modules from the Forge.
Correct errors introduced by using latest apt module

Since librarian-puppet had locked to old versions of Forge modules
but puppetlabs_spec_helper is now pulling the latest version,
there's this incompatibility to take care of in the test suite.
Extend Travis test matrix

* Add ruby 2.1.0
* Add back ruby 1.8.7 as allowed failure - shows test results
  but won't mark build as failed
* Enable fast finish - quick feedback on failed builds
* Make test matrix explicit so it's easier to tell what's included
  in the matrix, instead of excluding certain combinations
Add validate and lint tasks to travis script
Disable noisy/unneeded puppet-lint checks

* disable '80 characters check' - this is pretty useless and noisy
* disable 'class inherits from params class' check - is for puppet 2.6 which isn't supported
Fail on lint warnings from now on

Should improve PR quality and eliminate need for PRs to fix
any future lint issues
Fix remaining lint warnings
Merge pull request #377 from 3flex/modernize-travis

Improve test suite (Travis updates, librarian-puppet removal, better utilize puppet-lint)