Merge pull request #24 from williamboman/fix/immutable-dep

dep: downgrade immutable to ~3.7.4 to facilitate deduping

Author: mxstbr

package.json

@@ -38,7 +38,7 @@
     "detect-indent": "^4.0.0",
     "detect-newline": "^2.1.0",
     "ends-with": "^0.2.0",
-    "immutable": "^3.8.1"
+    "immutable": "3.x"
   },
   "devDependencies": {
     "babel-preset-es2015": "^6.6.0",