No error-throw promise

In chrome console:

p = new Promise((resolve, reject) => reject(33)) // Uncaught (in promise) 33

In thiis repo:

p = new PromiseJ((resolve, reject) => reject(33)) //  promiseJ<rejected:33>

Asynchronous `then` promise

Fix v0.0.1 synchronous then issue.

Example:

p = new PromiseJ(() => {})
p.then().then();  // working

p = new PromiseJ(() => {})
setTimeout(() => {
  p.then().then();  // working
})

Synchronous `then` promise

all then methods should be called Synchronously.

Example:

p = new PromiseJ(() => {})
p.then().then();  // working

p = new PromiseJ(() => {})
setTimeout(() => {
  p.then().then();  // not working
})