Fix timeout by bumping bdd interface

[Suite level timeouts](http://visionmedia.github.io/mocha/#suite-specific-timeouts) like:

``` js
describe('a suite of tests', function(){
  this.timeout(500);  // <------ This

  it('should take less than 500ms', function(done){
    setTimeout(done, 300);
  })
})
```

Stopped working for me when I require mocha-fibers.  Looks like the BDD interface has changed a bit since this file was copied.  I tried layering the fibers wrapping on top of the interface exported by mocha to avoid future synchronization issues.  Works for all my tests.  Whatcha think?  Also, thanks for writing this.