Merge pull request #275 from joenoon/use-hash-new-workaround

Cleaner workaround for RM-203
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.