Spinner lite

This spinner only uses GPU-accelerated transforms for its animations. Here's how the animation works:

* An arc is formed by two semi-circles (`div.circle` with colored top- and right-borders), `.left` and `.right`.
* There are a total of 8 semi-circles - 4 for each side, and 2 for each color of the spinner.
* Each semi-circle is rotated and faded in and out of view within a `div.circle-clipper`, which is half the width of a semi-circle and has `overflow: hidden`
* The two `div.circle-clipper` are adjacent, so it appears as if the two semi-circles form one arc.
* The two `div.circle-clipper` are within `div.circle-container`, which rotates at the same rate as the expand/contract animation so it appears as if the arc is always fixed on it's left or right end.
* The `div.circle-container` is within `div.container`, which rotates at a linear rate and adds "randomness" to the spinner.

## Compatibility
The spinner works in the active mode on the latest of the four browsers. ~~There are some issues in IE11 specifically when you toggle the active state of the spinner (which is fixed by simply opening the inspector and highlighting the affected elements !?!)~~ **Update:** Fixed by setting `animation: none` when inactive.