Promise support (Purposal)

Would be great to support Promises and also keep callback support.

I purpose something where memcached.gets('foo', function); would still work as today and memcached.gets('foo'); would return a Promise object that rejects on error and resolves on success. What do you think ? I can make a PR if there are interest.

[k0ff33]

That would be really great! I have an async/await flow in my server and at the moment I have to use Node 8 util.promisify functionality to enable promises.

const { promisify } = require('util')
const Memcached = require('memcached')

const memcached = new Memcached(process.env.MEMCACHED_URL)

const memcachedGet = promisify(memcached.get).bind(memcached)
const memcachedSet = promisify(memcached.set).bind(memcached)

module.exports = {
  get: memcachedGet,
  set: memcachedSet
}

[elegisandi]

@mapleeit would you mind creating new release with the promise-based support? thanks.