trait/promise: promise/A+ implementation as trait

Still needs to be made compatible with jQuery Deferred for maximum
usefulness.
trait/promise: renaming promise() to thenable()

It is only useful for returning an object with a then() for chaining
with other Promise/A+ implementations.

This is to free promise() to chain with jQuery's Deferred implementation
trait/promise: jQuery compatible .promise()
Built for promises

Closes #30
0.2.0
Merge pull request #34 from Aintaer/master

Promise Trait implementation
Closes issue #30