Changes "dashize" for "snakeCase" to make the generated SCSS file match the class in the widget.

We're using the framework at our office and it looks great. 

![dashboard](https://f.cloud.github.com/assets/486325/136483/c582daf4-714c-11e2-9de5-9e170cf3868f.jpg)

It just bothered me that when I created widgets with more than one word in the name, the first generated SASS file and the widget's class didn't match.

You can see it if you run:
```
$ dashing g widget PowerRanger
```

Then go to ./widgets/power_ranger/power_ranger.scss and see:
```
.widget-power_ranger {
}
```

Happened to me that I started adding CSS but nothing changed. Some time after I figured that the class that was generated into the SASS file was not right, better, the class given to the widget's element wasn't the same.

```
<div class="widget widget-power-ranger"></div>
```

This fixes that by changing "power-ranger" to "power_ranger" in the class of the widget.

That's all.