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.