History
============
0.0.9 (2015-09-15)
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- Sortables can now be nested

0.0.4 (2015-02-05)
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- Pure JS files for both client-side only use and webpack/Browserified bundles.
- Added `sensitivity` to Sortable to define how far from the center of an item you can drag before it re-sorts.
- Added `getPlaceholderContent()` for components with SortableItemMixin to replace placeholders with custom components (example in "simple").

0.0.3 (2015-02-04)
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- Horizontal sorting
- `sinkUndraggables` and `floatUndraggables` for modifying undraggable behavior