add [] and []= operators to state and mutate

[catmando]

so you can do things like
state[my_var]
and
mutate[my_var] = 12

etc...

This is a working monkey patch:

class HyperStore::StateWrapper < HyperStore::BaseStoreClass
  def [](x)
    __send__(x)
  end
end

class HyperStore::MutatorWrapper < HyperStore::BaseStoreClass
  def [](x)
    __send__(x)
  end
  def []=(x, y)
    __send__(x, y)
  end
end

Need to add a test spec is all...