(feat) Added convenience impl of Middleware for controller functions.
Merge pull request #63 from reem/feat/controller-middleware

(feat) Added convenience impl of Middleware for controller functions.
(feat) Converted Furnace to Chain.
(feat) Converted StackFurnace to StackChain.
(feat) Converted Iron to use Chain.
(feat) Changed exports to work with Chain.
(feat) Implemented Middleware for Box<Chain>
(feat) Converted examples to use link.
(doc) Brought README up to date for Chain.
(doc) Changed smelt to link.
(doc) Changed from Furnace to Chain.