Code Coverage Support added

Expresso's Code Coverage support added to nodeunit

inorder to use it.
you've define requires as follows
 var a = require('a');
instead 
 var a = require('../lib/a')

Then it'll automatically detect this and added code coverage support.
and display the summery.
If you need more information add -cr option
 eg:- nodeunit -cr tests 

if you need to ommit Code Coverage you can use -ci option
 eg:- nodeunit -ci tests

And this will not affect existing tests written in Nodeunit and above little require modification adds the coverage support