chore(package): update primus to version 7.2.0

package.json

@@ -37,7 +37,7 @@
     "istanbul": "~0.4.5",
     "mocha": "~5.1.0",
     "pre-commit": "~1.2.0",
-    "primus": "~7.1.0",
+    "primus": "~7.2.0",
     "ws": "~5.1.0"
   }
 }