correct the example code on README.md, and refactor deferred.js, sperate

correct the example code on README.md, and refactor deferred.js, sperate into two object with Promise and Deferred, and Promise is the property
of Deferred Object

hi, I just searched your project when I'm googling arount some async library, and it's simple and clear, but I thought it's better to seprate the entire defered object into deferred and promised object, and it will also make chaining promise easy to implement, so I just did it.

don't feel angry if you thought I changed your code, feel free to ignore this RP if you don't like it.
but the code sample on the readme need to be update :)