docs: added details about progress event fire order
change: zero duration tweens now have no after state

instead they only reach "DURING".
This is in accordance with the new progress event logic.
updated: examples
change: state detection in progress method

made it easier to differentiate between zero duration scenes and
regular ones…
fixed: small bug that occurred through shift event
added: scene destroy event
changed: skrollr desc
feature: dynamic duration

now the duration option can also be a function. It is periodically
called to update the duration using the functions return value
updated: responsive duration example
bugfix: fixed 2 pin issues

Fixed the width of the pinned element collapsing, when no width was set:
https://github.com/janpaepke/ScrollMagic/issues/63
https://github.com/janpaepke/ScrollMagic/issues/94

Fixed IE9 bug, of pinned element positioning
added: some new tests