RSpec unit tests for evaluator.rb

Converted unit tests for evaluator to RSpec.
Refactored EvaluationResult and its subclasses.
Extended Evaluator to be able to parse all geospatial queries (they don't need much handling though).
Removed stale lib/evaluator.rb file.
Merge pull request #49 from jonasz/master

RSpec for evaluator.rb
Merge branch 'master' of github.com:brandonblack/mongo-tools