Remove asm.js-based simplex-noise for faster performance on Firefox

asm.js currently has a massive performance hit when crossing the
asm.js/JavaScript boundary, which happens on every simplex noise call,
so it is noticeably slower than pure JavaScript for chunk generation.
Revert to the 2.1.1 simplex-noise release (without asm.js) to fix this.

jwagner/simplex-noise.js#5

package.json

@@ -14,7 +14,7 @@
   ],
   "dependencies": {
     "voxel-trees": "~0.1.0",
-    "simplex-noise": "git://github.com/deathcap/simplex-noise.js.git#eba7c7e7599ef58ac5d7eef7ee81eb2505aac56c",
+    "simplex-noise": "^2.1.1",
     "alea": "0.0.9",
     "webworkify": "~0.1.0",
     "unworkify": "git://github.com/deathcap/unworkify.git#31f62e3536ecb0f53f864e3073f5ce1d565174c7",