I'm try run examples/simple.rb in master but throw this error: ``` entropy': undefined method `sum' for [2, 3, 1]:Array (NoMethodError) ``` Try gem version 0.5.0 and work find, maybe it introduced in pull request [#32](https://github.com/igrigorik/decisiontree/commit/846448acd635e192828da64eb0d17ab7435c45a2)