Update rspec-puppet to 1.0.1

Pin rspec because rspec 3 has a load of deprecation notices relating
to custom matchers.
Set osfamily during tests

This gets around modules that check the platform of the thing
they're running on and then fail.
Add basic test for DNS class

Ensure that the file is formatted correctly.
Upgrade puppet-lint

- Always report on the problems
- Remove the disable of the double quoted string check
Merge pull request #558 from alphagov/testing-and-linting

Improved testing