Rename prepublish script to prepublish-lib as it works incorrectl…

…y with Yarn.

See yarnpkg/yarn#3209

package.json

@@ -11,7 +11,7 @@
     "test": "jest",
     "test-watch": "jest --watch",
     "build": "babel src --out-dir lib",
-    "prepublish": "rm -rf lib && babel src --out-dir lib"
+    "prepublish-lib": "rm -rf lib && babel src --out-dir lib"
   },
   "standard": {
     "globals": ["jest", "test", "expect", "it", "describe"]