Option to hide pager if it's got more than one page.

I didn't want the pager to show if there is only one page. Auto scroll should also get disabled.

```html
<div class="slider">
  <div class="slide"><img src="http://placehold.it/200x150&text=FooBar1"></div>
  <div class="slide"><img src="http://placehold.it/200x150&text=FooBar2"></div>
</div>
```

This element is not large enough to warrant pages.

```javascript
$('.slider').bxSlider({
    slideWidth: 200,
    minSlides: 4,
    maxSlides: 5,
    slideMargin: 10,
    auto: true
 });
```

To keep backwards compatibility I introduced a new property ```autoHidePager``` that defaults to false

 ```javascript
$('.slider').bxSlider({
    slideWidth: 200,
    minSlides: 4,
    maxSlides: 5,
    slideMargin: 10,
    autoHidePager: true,
    auto: true
 });
```

If you set it to true, you will see the pager disappear if there is only one page. It will also disable the dynamic scrolling started by the ```auto``` keyword.

http://jsfiddle.net/digiguru/XakZ6/1/embedded/result/

I'd be happier if this default was ```true``` but that would make it a breaking change.