Change be true to be_truthy and upgrade chefspec version

There is an issu with RSpec 2.99 breaking backwards compatibility so I upgraded to ChefSpec 4.0. This resolved a failure `uninitialized constant RSpec::Matchers::BuiltIn::RaiseError::MatchAliases (NameError)`

`be_true` was also deprecated so I changed them all to `be_truthy`. I originally had it as `be true` but that wants to match exactly `true`, but in our tests, we are getting (string) "true".