Transducers, mori.reducers

Adds mori.reducers namespace, moving r prefixed fns
to this namespace. Adds tranduce and related transducer
functions.
Merge pull request #116 from tgriesser/cmp

Expose comparison functions, fixes #112
Merge pull request #115 from tgriesser/transducers

Transducers, mori.reducers
Basic protocol support for JS objects via mori.extend
Update .extend api
Add IIndexed protocol