chore(package): update dotenv to version 6.1.0

Closes #102

Author: greenkeeper[bot]

package.json

@@ -19,7 +19,7 @@
   "devDependencies": {
     "ava": "^0.20.0",
     "coveralls": "^2.13.1",
-    "dotenv": "^4.0.0",
+    "dotenv": "^6.1.0",
     "nyc": "^11.0.3",
     "rimraf": "^2.6.1",
     "snazzy": "^7.0.0",