Make first scrollspy active by default if no other scrollspies active

[thepuzzlemaster]

Potential implementation of #128

If you are above all scrollspies, the first one is active.

@oblador the tests are failing, but I'm not sure if that's because of this PR or something different. It looks like the latest build on github doesn't include the $interval code as when I do a build, those changes are showing up as new. Would you mind providing some assistance for me in that regard?