chore(package): update chai-immutable to version 2.1.0

Closes #46

Author: greenkeeper[bot]

package.json

@@ -43,7 +43,7 @@
     "babel-preset-es2015": "^6.24.1",
     "chai": "^4.1.2",
     "chai-as-promised": "^7.1.1",
-    "chai-immutable": "^1.6.0",
+    "chai-immutable": "^2.1.0",
     "chai-string": "^1.4.0",
     "eslint": "^5.0.0",
     "hoek": "^5.0.3",