chore(package): update dotenv to version 6.2.0

Closes #99

Author: greenkeeper[bot]

package.json

@@ -17,7 +17,7 @@
   "devDependencies": {
     "ava": "^0.25.0",
     "coveralls": "^3.0.0",
-    "dotenv": "^5.0.0",
+    "dotenv": "^6.2.0",
     "nyc": "^11.4.1",
     "reshape-standard": "^3.3.0",
     "rimraf": "^2.6.2",