Ignore exit(1) from Puppet 3.4 parser face

The parser face now exits with a non-zero exit code if it encounters any
errors in the manifests it is testing:

puppetlabs/puppet@1a526d0940d8cb39161c638c17f4d6813d0c1a17

This is useful for the `puppet parser validate` CLI. But it's not useful to
us here, so catch and ignore the `SystemExit` exception.
Add 3.4 as a puppet version for travis to test.
Merge pull request #6 from gds-operations/puppet_34_support

Ignore exit(1) from Puppet 3.4 parser face