Switched from percents to pixels for animation keyframes.

This leads to more consistent train speeds with window size.
(Will still be minor changes in speed with window size, but do not
believe these are visually significant.)
Altered look of background lighting gradient behind trains.

Light is now concentrated strongly at the front of the train, with
weaker peaks in the center of each carriage.
Is this an improvement?
Merge branch 'master' into gh-pages
Updating gh-pages index to display trains with improved bg gradients.