Add Array.prototype - like iterator methods to im.object and im.array

[hughfdjackson]

Add support for the following on both im.object and im.array:

• every
• some
• forEach
• map
• filter
• reduce
• reduceRight

See http://es5.github.io/#x15.4.4.16 onwards.

[hughfdjackson]

reduceRight omitted for objects, since they provide no ordering guarantee, and therefore have no meaningful semantic for what it might mean.

Todo:

• Double check that they stick to the API provided by their native cousins where it makes sense
• Document them