Fix Issue #153 Wrong contentInsets when connected mouse

[m1entus]

No description provided.

[dani-mp]

Hi, @m1entus. Thanks for the fix, you're awesome. I couldn't reproduce it in my Mac, but a colleague told me about it. It was happening after item selection, very weird.

Anyway, just setting the scroller type to .Overlay did the fix for me, without having to register for the notification.

[m1entus]

Anyway this will resolve issue when scroller is set to Legacy, end if you connect/reconnect mouse again notification will be called and correct document size will be set ;)

[jwilling]

As this library is 64-bit only, there's no need to bridge between NSRect and CGRect. They can be used interchangeably. So it could just look like this:

if (!CGSizeEqualToSize(documentView.frame.size, self.contentSize)) {

[jwilling]

Thank you for spending the time to put this together. ✨

I just have a couple of comments and questions before I merge this.