workaround is actually incorrect.  hash.default = [] means every
key will use the same array, which doesnt work.  added a spec
to make sure this case is caught even though its a strange case.
reverted to code before the workaround, since after adding further
specs, there is no way to avoid a retain cycle with the current
version of rubymotion. it sounds like the next version of
rubymotion will address this.  when it does, these specs should
pass.
not using proxy in this spec
Merge pull request #276 from joenoon/use-hash-new-workaround

Undo Hash.new workaround, add memory specs