fix(package): Set minimum node version to 4

See semantic-release/semantic-release#433

Author: pvdlg

package.json

@@ -47,7 +47,7 @@
     "tempy": "^0.2.0"
   },
   "engines": {
-    "node": ">=8"
+    "node": ">=4"
   },
   "eslintConfig": {
     "extends": [