Fix swiping

Fixes issue #31.

This is a major version bump because it represents a breaking change for anyone who enabled swiping by manually adding CSS class scrtabs-allow-scrollbar to a parent element of the scrolling tabs. That will no longer trigger a horizontal scrollbar for the tabs, so swiping will not be active. To enable swiping, you will instead need to pass in option enableSwiping: true.

If you already enabled swiping by passing in option enableSwiping: true, this change should not break anything, and should, in fact, fix a problem.

Swiping functionality is now handled via code rather than the browser's built-in scrolling with a scrollbar due to conflicts that occurred if, on a touch screen, you performed a combination of swiping and pressing the scroll arrows.