From a subclass, Vector#clear returns an instance of the subclass
Add more specs for Vector#set
Moderate performance boost for Vector#set
Small tweak to EmptyVector initialization (to match Hash and Set implementation)
Differentiate between Hamster::Vector#== and #eql?
Vector.new makes defensive copy of a small, non-frozen Array passed in as initializer
Big performance boost to Vector#to_a. It may return a frozen Array (so does Ruby Array#to_a)