[change] StyleSheet performance rewrite

Improves StyleSheet benchmark performance by 13x. Removes undocumented
`StyleSheet.resolve` API.

Typical mean (and first) task duration.

[benchmark] DeepTree: depth=3, breadth=10, wrap=4)
  -master  2809.76ms (3117.64ms)
  -patch     211.2ms  (364.28ms)

[benchmark] DeepTree: depth=5, breadth=3, wrap=1)
  -master   421.25ms (428.15ms)
  -patch     32.46ms  (47.36ms)

This patch adds memoization of DOM prop resolution (~3-4x faster), and
re-introduces a `className`-based styling strategy (~3-4x faster).
Styles map to "atomic css" rules.

Fix #307

package.json

@@ -24,6 +24,7 @@
   "dependencies": {
     "animated": "^0.1.3",
     "array-find-index": "^1.0.2",
+    "asap": "^2.0.5",
     "babel-runtime": "^6.11.6",
     "debounce": "^1.0.0",
     "deep-assign": "^2.0.0",