Added :\ to EquiSet.
Added ++, --, /: and :\ to SortedEquiSet.
Added 3 addString methods to EquiSet.
Added aggregate method to EquiSet, and ++ method that takes another EquiSet to support aggregate usage.
Added -- method that takes another EquiSet to EquiSet.
Added thisEquiSets. prefix to ++ method parameter in EquiSets and SortedEquiSets.
Added apply method to EquiSet.
Added andThen method to EquiSet.
Make EquiSet to extend Function1 and removed the andThen method.
Added canEqual method to EquiSet.
Added check for equality of equality field in canEqual implementation of EquiSet.