Mr/falkor Puppet 4 version, transparent support for arrays and vagrant-based tests

[Falkor]

Dear Tom,

Here are the changes I made to publish the ulimit module under my own namespace on Puppet forge (see svarrette/ulimit) while waiting for your own new release as per Issue #9.
I didn't want to touch it initially, but I couldn't prevent myself to extend the offered features and ensure a maximal scoring on Puppet Forge.
In short (sorry for the messy list of commits inherent to my internal versionning policy):

• Puppet String documentation and enhanced README.md
• minor corrections in metadata.json
• Integration of Vagrant-based tests (including. highly customizable Vagrantfile and provisioning scripts)
  • Enhanced tests in tests/
• Within ulimit::rule:
  • Support for String or Arrays (transparently) for the $ulimit_type and/or $ulimit_item parameters. Based on initial merge request of Jake Humphries aka Jake151 (yet I was not a fan of making it enfore the same array length)
  • Support for new parameters source and content