Add Set#new (so subclasses of Set can be instantiated)
Merge pull request #102 from alexdowad/set_subclassing

Add Set#new (so subclasses of Set can be instantiated)
Updated homepage in gemspec

Closes #105.
Added spec for Hamster::Set.new
Fixed bug in Set#difference (caused by merging incompatible commits)
Fixed typo in README
Boost performance of List#car, #cdr, #cadr, #cdar, etc etc