fix megaraid_virtual_drives fact return value

Resolves this test failure:
  1) megaraid_virtual_drives on linux no adapters should be nil
     Failure/Error: Facter.fact(:megaraid_virtual_drives).value.should be_nil
       expected: nil
            got: ""
add future parser to travis matrix
make #verify_contents usage compatible with rspec-puppet > 1.0.1

The verify_contents method invocations have been updated to work with
rspec-puppet 1.0.1+ but are now incompatible with <= 1.0.1
https://github.com/rodjek/rspec-puppet/issues/235
Merge pull request #39 from jhoblitt/feature/future_parser

Feature/future parser