Fixed wrong behavior with before, between and after classes

Under certain circumstances it was possible that a skrollable had the
`skrollable-before` AND `skrollable-after` class.

This was caused by wrongly sorted keyframes, which caused skrollr to think that
the element was both before and after the last/first keyframe.
0.6.4
fixed crash in IE because no prefix is detected. fixes #220
0.6.5
fixed crash in IE because no prefix is detected. fixes #220
fixed nav example was jumping. fixed #224
added http://www.entropy-thegame.com/ to the list
added http://www.photo-mark.com/funhouse/chess/
don't assign skrollr.setStyle to a local variable because it breaks the IE plugin. fixes #199 (comment 18986949)
0.6.6
changed default for `edgeStrategy` to `set`
updated github.com to github.io links. fixes #212
added link to a simple jQuery plugin for refreshing skrollr. fixes #195
added new option `smoothScrollingDuration`. Fixes #218
0.6.8
Merge branch 'master' of https://github.com/Prinzhorn/skrollr

Conflicts:
	src/skrollr.js