v0.5.0

• smarter toString: call json.stringify if the object doesn't have a custom toString()
• add partial application (FunctionX.applyX)
• micro-optimizations in Vector
• fastpath for equality in case this===other
• hashmap.tostring, try harder to format the key nicely on toString()
• [behavior change] throw at runtime if given a hashmap key or hashset
  value without proper equality support. should only matter for javascript or typescript with casts/any use
• add lazy.map
• [api change] tuple.ofarray->tuple.ofpair, add ofarray which checks the number of elements
• make stream.ofarray private, although this has no effect on the transpiled JS code
  (please use Stream.ofIterator)
• add Lazy.toString
• add Either.liftA2, Either.liftAp, Option.liftAp
• make Option, Either, LinkedList and Stream union types instead of abstract classes, export the
  individual types (Some, None, Left, Right, EmptyLinkedList, ConsLinkedList,
  EmptyStream, ConsStream), make isEmpty, isLeft, isRight, isSome, isNone type guards.
• code samples in apidocs are now extracted and run as part of tests