Compatible with hashie 3

While trying to use berkshelf, varia_model was blowing up, due to a major version upgrade in Hashie.

Upon inspection, it seems like the file which was being required isn't even necessary.

Rather than forever constrain Hashie to an old version, let's keep up!

I also updated the specs to remove RSpec deprecation warnings when using version 2. These turn to failures in RSpec 3.