Add rake tasks to validate and lint files and check with Travis

This patch adds the ability to validate syntax of manifests, templates,
and ruby files in lib/ via `rake validate` and the linting of manifests
with puppet-lint via `rake lint`. These two commands are chained with
running the spec tests in Travis to ensure there are no syntax or style
issues.
Merge pull request #208 from ghoneycutt/add_validation

Add rake tasks to validate and lint files and check with Travis