Add support for promises

[dotlouis]

Now that Node supports Promises by default, it would be great to have them supported.
With a dual callback/promise non-breaking api.
You can either supply a callback, or don't and a promise will be returned.

Thanks

[robertjd]

Hi @dotlouis , thanks for the request! ES6 support in Node is really exciting :) We will find time in the future to add promises, in the meantime we are going to focus on moving this library to a 1.0 release (as we have to break some of our own APIs).

[deyceg]

@dotlouis If you can't wait for a 1.0 release; why not use https://github.com/petkaantonov/bluebird/?

const stormpath = require('stormpath')
const client = new stormpath.Client();

Promise.promisifyAll(client);

client
  .getApplicationAsync(...)
  .then(...)