Mod: update sticky.js to 2.9

Old version, 2.8, doesn't work with latest Chrome version.
See https://github.com/TEA-ebook/teabook-open-reader/issues/29
Mod: update references to sticky 2.9 instead of 2.8
Merge pull request #31 from CrEv/pr/sticky2.9

Broken demo: Mod: update sticky.js to 2.9