Mash#fetch with no default and Mash#fetch with nil default are different cases about hashie

[jch]

I think Mash follows the same behavior as Hash when the key doesn't exist:

irb(main):015:0> h = Hash.new
=> {}
irb(main):016:0> m = Hashie::Mash.new
=> #<Hashie::Mash>
irb(main):017:0> h.fetch(:foo)
KeyError: key not found: :foo
irb(main):018:0> m.fetch(:foo)
KeyError: key not found: :foo

Let me know if that's not what you meant.

[jch]

Oops, just re-read that more carefully and realized you had a 2nd argument. Interested in building a pull for this? It'd go along nicely with #93 that you opened.