minor: renamed Promise.js to make place for new implementation
New Promise Implementation based on Continuations

* very elegant,
  especially in construction of new promises from other ones
* `new Promise` constructor with synchronous, asynchronous and
  continuative resolution
* monadic Promise::map, Promise::chain and Promise.of methods
* continuations allow for minimal callstack size
* built-in support for multiple arguments
* uses setImmediate for asynchrony