OrderedHash should not pretend to be an Array

The ActiveSupport::OrderedHash that comes back from such methods as #group_by looks, in script/console, indistinguishable from an Array, which makes me want to call methods on it like an array, which leads to pain and confusion. Attached is a tiny patch that adds an #inspect method to ActiveSupport::OrderedHash that produces output that looks like this: http://pastie.org/364930 Goal is to make it clear that you're dealing with an OrderedHash, but also to encourage you to think of it as having hash-like rather than array-like indexing.