Added addURL method

This just increases the usability of the class and for basic usage means CURL is almost irrelevant from the library as-in it does not matter that it is CURL, it could be any method of getting multiple URL's...
Simplified example

Simplified example so that anyone could use regardless of level of experience
Update README
Update example.php

forgot to keep vars in... added now oops...
fixed doof

Forgot to check the tiny area of code when I renamed a variable... hey it was late...
Merge pull request #12 from Lewiscowles1986/master

Added simpler syntax usability for simply including getting instance and then adding URL's