Make frozen entity lists immutable.
Merge pull request #97 from alxhub/immutable-lists

Make frozen entity lists immutable.
Replace streamy SetMultimap with implementation from Quiver.
Merge pull request #101 from cbracken/quiver-multimap

Replace streamy SetMultimap with Quiver implementation.
Moved off Int64.fromInt() to default constructor
Merge pull request #103 from cbracken/fixnum-ctor

Move off Int64.fromInt() constructor to Int64() constructor