Disable Resolve on Return

Disable auto-resolve functionality on return keyword. Any asynchronous function that need to be resolved before returning values can be accomplished by appending yield after return (e.g. return yield asyncFunctionHere())

Compatibility with Node.js v4

Compatible to use with Node.js v4 which does not support let keyword without explicit 'use strict' directive.

Rewrite Setlist from stratch

Implements new function such as promisify(), callbackify(), and proxify() (see README for details and usage), drop non-functioning timeout function in generator runner.