Added support to a custom LongPressGesture instead of LongPressGesture used for the highlight of the cell 

HI Christopher,

First of all, thanks for this great project. I've been using SWTableViewCell on almost 2/3 of projects of mine.

Recently I've came across a situation where I needed to recognise press & hold gestures on a SWTableViewCell and as far as I've googled it, it seems like there is a SWLongPressGestureRecognizer property used to highlight of the cell (which is how iOS7 Mail application works) that unfortunately mess up with a custom UILongPressGestureRecognizer defined by developer.

I've also seen that on a couple of issues ( #164 , #156 ) a few developers were able to use their on UILongPressGestureRecognizer by taking out this line:

    [self.cellScrollView addGestureRecognizer:self.longPressGestureRecognizer];

So I've decided to create a IBInspectable property ( which shows up on storyboard as a property ) that let the developer choose whether they want to use the internal longPressGestureRecognizer or not like below:

![screen shot 2014-11-07 at 3 46 31 pm](https://cloud.githubusercontent.com/assets/1011868/4957592/0eb579ac-66a6-11e4-8d8f-6e21765e4f9f.png)

If you think this is a fair property to be used on your framework, please accept my pull request.

Best Regards

Paulo Miguel Almeida