fix(package): update qs to version 6.9.1

Closes #38

Author: greenkeeper[bot]

package.json

@@ -23,7 +23,7 @@
 	"main": "src/index.js",
 	"dependencies": {
 		"is-stream": "1.1.0",
-		"qs": "6.5.1",
+		"qs": "6.9.1",
 		"body": "5.1.0",
 		"accepts": "1.3.5"
 	},