Memory warning observer never deleted

[banaslee]

I'm still not able to contribute to the project with code but I've found that the button never deletes himself as an observer of memory warning notifications.

This was leading my app to crashes when memory was low.

I suggest changing the dealloc code to

- (void)dealloc
{
    _color = nil;
    _buttonCornerRadius = nil;
    kFontAwesomeStrings = nil;

    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidReceiveMemoryWarningNotification object:nil];
}

[jessesquires]

thanks @banaslee ! good catch