Remember any call to setOptions() and authorize partial options application...

So, here is my use case :

Different calls to `setOptions()` won't recall the precedent options.
That's not what we usually expect, and it requires that we re-pass every defined option value when we want to only change one. 

The basic use case is :

```js
// Let's be pedantic..
marked.setOptions({pedantic: true});
var result1 = marked(pedanticInput));  

// Let's add some highlights 
marked.setOptions({
  highlight: function(code, lang) {
    console.log("How wonderful! You talk " + lang);
    return "<blink>" + code + "</blink>";
  }
});
var result2 = marked(pedanticInput);  // << i still expect to be pedantic here ! 
                                    // but in fact, i'm not even gfm (the defaults were erased) 
```

The test suite with the *current* marked version can be found here : http://codepen.io/zipang/pen/zIoaB
And the same test suite with marked patched is here : http://codepen.io/zipang/pen/cGkIs