= QueryHash

A QueryHash is a Hash that provides open access much like an OpenHash, but it limits readers
to bang and query methods (i.e. method ending in `!` or `?`).

  q = QueryHash.new
  q.a = 1
  q.b = 2
  q.a?.assert == 1
  q.b?.assert == 2

By default keys are converted to strings.

  q.assert == { "a"=>1, "b"=>2 }

A QueryHash is compatible with Ruby's standard Hash in every other respect.

