Modestmaps

- enforce limits when zooming and panning so that map functions are correct
when returning and before the deferred draw call using getFrame

- revert to tmcw's original getFrame (simpler version broke in Chrome)

- revert Coordinate.toKey to string joining
- fix up utils.js functions so that tests run again
- modify double-tap thresholds and adjust onPinched behavior
- a few more cleanups in TouchHandler (mainly to use MM.Point functions)

- many tiny formatting/syntax fixes; thx JSHint!
- MM.moveElement is used for tile positioning
- MM.moveElement detects and uses CSS transforms wherever possible
- MM.bind is used for function binding instead of awkward closures
- MM.getFrame is used to request redraws
- MM.getFrame uses provisional requestAnimationFrame implementations if possible
- TouchHandler is in the default build of modestmaps.js
- Coordinate.toKey() is clever again ;)

Thanks to tmcw for the majority of these contributions. They were contributed
on a branch, hence only one minor version number bump. As far as we know this
should all be backwards compatible. If we're mistaken, please file an issue at
https://github.com/stamen/modestmaps-js/issues

Note also that we've now got fairly decent node.js support for the core MM.js
classes, and there's an example of how to use Modest Maps with node-canvas to
render static map images from a tiled data source. "npm install modestmaps" for
node.js fans :)

- Mouse handlers refactor: while MouseHandler is still available for adding
all handlers to the map, double-click, zoomwheel, and drag handlers are
available individually.
- Broken images that result from image loading errors are no longer added to
the map.

- Unimplemented abstract methods throw exceptions instead of calling `alert()`