Removed Aggregatables and moved aggregation methods into Collection.
Added Collection::product for getting product of values in the collection.
Added Collection::rest which takes rest of the elements except first.
Added Collection::partition.

Splits a collection into a pair of two collections; one with elements that
match a given predicate, the other with the elements that do not.
Added Collection::filterNot for filtering elements which do not match a given predicate.
Added Collection::isEmpty for checking whether the collection is empty.
Changed rest() to maintain index associations to be in line with other methods.
Updated documentation.
Fixed lists.
Moar documentation.
Merge pull request #7 from xi-project/move-and-groove

Added methods to Collection and updated documentation