For a TimedItem with infinte duration, the transformed time should should be equal to the directed time

Currently, in order to calculate the transformed time from the directed time,
we divide by the duration to get the time fraction, apply the timing function,
then multiply the result by the duration. This means that if the duration is
infinity, the transformed time is always zero, so the TimedItem's effect or
children will not play.

For a group, this behavior is probably unexpected. Consider the following
example ...

document.timeline.play(new ParGroup([
  new Animation(foo, bar, {iterations: Infinity, duration: 2}),
  new Animation(foo, bar, {iterations: Infinity, duration: 3}),
]));

A reasonable expectation is that both animations will repeat inefinitely, but
currently, neither will play. Note that in this example, the
'iterations: Infinity' can't easily be moved to the ParGroup because the
animations have different durations.

Instead, if the duration is infinity, we should set the transformed time to the
directed time. This means that the childrens' inherited times will progress as
expected, so they will play.

Note that the time fraction will remain zero, so an Animation with infinite
duration will still not play.
add initial version of index page
add initial version of index page
add initial version of index page
initial demo landing page
add the zeppelin
refactor demo directory
Revert "refactor demo directory"

This reverts commit 4454f3c9fc7241a188d4d0f046cf5088d5929e01.
add viewport tag
add viewport height
better responsive design
even better responsive design
clean up demo page code
remove link to cloud.css and correct zeppelin initial position
fix some spacing issues
add touch demo and fix prefixes
remove car demo
fix animation, works with unprefixes transforms
Merge pull request #489 from maxh/master

Add Web Anim demos landing page
Fix timing for Safari