Promisifies all the selected functions in an object

 Some features of this module:
  - Preserves function names
  - Uses a native promise implementation if available and tries to fall back to
    a promise implementation such as bluebird
  - Converts multiple arguments from the callback into an Array, also support
    change the behavior by options.multiArgs
  - Resulting function never deoptimizes
  - Supports both callback and promise style
 An added benefit is that thrown errors in that async function will be caught
 by the promise!
 .
 Node.js is an event-based server-side JavaScript engine.