Update dependencies to enable Greenkeeper 🌴 (#558)

* chore(package): update dependencies

* docs(readme): add Greenkeeper badge

Author: greenkeeper[bot]

README.md

@@ -1,5 +1,7 @@
 ## Node MySQL 2
 
+[![Greenkeeper badge](https://badges.greenkeeper.io/sidorares/node-mysql2.svg)](https://greenkeeper.io/)
+
 [![NPM Version][npm-image]][npm-url]
 [![NPM Downloads][downloads-image]][downloads-url]
 [![Node.js Version][node-version-image]][node-version-url]

package.json

@@ -54,7 +54,7 @@
     "lru-cache": "^4.0.1",
     "named-placeholders": "1.1.1",
     "object-assign": "^4.1.1",
-    "readable-stream": "2.2.8",
+    "readable-stream": "2.2.9",
     "safe-buffer": "^5.0.1",
     "seq-queue": "0.0.5",
     "sqlstring": "^2.2.0"