Add unit tests and travis-ci support

This patch includes some very basic and initial unit testing using rspec-puppet
and for the case of facts, just normal rspec.

I've taken a very light approach here as rspec-puppet can be quite combinatorial
when one gets carried away. For now I've just added basic compile failure
detection effectively for classes and defined resources. As we continue to work
on the code and find regressions this work can be expanded.

For facts and functions I've also taken a basic approach for now.

One little thing I did change, was the strange string that the fact returns
when the default version is undefined. Instead of an error message I've just
returned the string 'unknown' which is more in line with other facts I've seen
in the wild, and to be quite honest 'unknown' is fairly self-explantory. Since
a fact isn't an error reporting message this seemed more appropriate, and looked
nicer in the rspec test.

As far as travis-ci support, I've added the same configuration that @jmmcune
came up with for stdlib which is pretty light and reasonable standard now we
propogated that to 4 or so other modules in the puppetlabs/ namespace. It should
work out of the box.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #115 from kbarber/ticket/master/unit_tests

Add unit tests and travis-ci support