Add ability to work with Tabs and in other cases

[NaikSoftware]

Improved gesture recognizer to intercept only used events.
Added ability to change canSwipe from route.

  @override
  void initState() {
    super.initState();
    _tabController = TabController(length: _tabCount, vsync: this);
    _tabController.addListener(() {
      if (mounted) {
        final canSwipe = _tabController.index == 0;
        SwipeablePageSettings.of(context).canSwipe = canSwipe;
      }
    });
  }

This PR fixes #12 and #6

I found another variant to manage canSwipe flag and it also working.

[JonasWanke]

This is now published as part of v0.2.4. Thanks for contributing!