Add test for Issue #69
Force focus before testing visibility on focusable elements.

[Finishes #65]
Move GUI only tests into their own test file
Merge pull request #68 from ckundo/dropdown-focus-test

Force focus on elements before checking if they are visible (e.g. skip-nav links)
Fix issues: crash when overlappingElements was null, and text not being computed for hidden elements
Merge pull request #70 from alice/crash

Fix issues: crash when overlappingElements was null, and text not being ...
Check for scrollbars on parent elements
Check scrollWidth; check for overflow = 'hidden' or 'scroll'
Check for clipping by container elements
Merge pull request #71 from alice/scrollArea

Check for focusable element inside scroll area of non-body parents
Check for body element in axs.utils.canScrollTo
Use instanceof check instead of tagName
Merge pull request #72 from alice/scrollArea

Check for body element in axs.utils.canScrollTo()