fix(package): update axios to version 0.18.0

Closes #22

Author: greenkeeper[bot]

package.json

@@ -20,7 +20,7 @@
   "author": "Jon Nordby <jononor@gmail.com>",
   "license": "MIT",
   "dependencies": {
-    "axios": "^0.16.1",
+    "axios": "^0.18.0",
     "bluebird": "^3.4.1",
     "body-parser": "^1.15.2",
     "coffee-script": "^1.10.0",