Adding a minify option to compress whitespace.

Addresses #38.

Setting the `minify:true` option would compress consecutive whitespace characters into a single character.

Before:

```html
<div>
    <p class="mini   doge">Wow</p>

        <span>So save</span>
    <p>Much compress</p>
</div>
```

After:

```html
<div> <p class="mini doge">Wow</p> <span>So save</span> <p>Much compress</p> </div>
```