Fixed detection of orientation support

Hi,

CoffeeScript's ``in`` keyword generates an __indexOf() search for "orientationchange" in the window object. I assume this is not what you intended - therefore I changed it to

```coffeescript
_supports_orientation = "onorientationchange" of window
```

Which translates to (JavaScript):

```javascript
var _supports_orientation;
_supports_orientation = "onorientationchange" in window;
```