Add guard-yard to development dependencies
Get rid of Dataset grouping functions
Remove parameter handling in Comparator
Fix comparator score method in test helper
Change Comparator.register to require name
Simplify Compare
Add Dataset#primary_key for convenience
Add default Comparator#score_datasets implementation
Remove Comparator#score_datasets implementation

- the default implementation should be handled in the runner for the
  sake of speed
- added Comparator#type
- require subclasses of Comparator to define both score_datasets and
  score_dataset if they don't define the score method
Add :equal_to operator to Compare

- using :equal_to in Compare switches to advanced comparator mode
- use to_expr in Compare#score instead of name
- implement sorted comparisons in Compare#score_datasets and
  Compare#score_dataset for :equal_to
Convert Strcompare to new Comparator style
Go back to using #name in Compare
Convert Within to new comparator format
Use name instead of expr in Strcompare
Rip the guts out of Configuration

- delete the DSL
- use method_missing to add comparators
Add Comparator#score_and_notify
Configuration tweaks

- add default value for dataset_2 in #initialize
- rename comparisons to comparators
Rewrite SingleThreadedRunner

- rename 'runner' directory to 'runners'
- result set is now passed in as an argument to Runner
Use add_score method for result set observation
Remove Comparator.comparator_name