Add aliases so full Hash spec works with Hashie::Mash.
Add aliases so full Hash spec works with Hashie::Mash.

Hashes have a number of alternates to .has_key? which are shown at
http://www.ruby-doc.org/core/classes/Hash.html#M000767 This commit
adds those aliases for Hashie::Mash#key?
intridea/hashie,benjaminoakes/hashie,michaelherold/hashie,michaelherold/hashie,dblock/hashie,marshall-lee/hashie,intridea/hashie,marshall-lee/hashie,dblock/hashie