chore(package): update microstates to version 0.15.1

Closes #28

Author: greenkeeper[bot]

package.json

@@ -43,7 +43,7 @@
     "babel-core": "7.0.0-bridge.0",
     "babel-jest": "23.6.0",
     "jest": "23.6.0",
-    "microstates": "^0.13.0",
+    "microstates": "^0.15.1",
     "react": "^16.8.0",
     "react-dom": "^16.8.0",
     "rollup": "1.2.0",