fix: reinstate har-validator (#15)

Author: grxy

package.json

@@ -34,6 +34,7 @@
     "extend": "~3.0.2",
     "forever-agent": "~0.6.1",
     "form-data": "~2.3.2",
+    "har-validator": "~5.1.3",
     "http-signature": "~1.3.6",
     "is-typedarray": "~1.0.0",
     "isstream": "~0.1.2",