fix(package): update yargs to version 15.0.1

Closes #106

Author: greenkeeper[bot]

package.json

@@ -21,7 +21,7 @@
     "inquirer": "^6.5.0",
     "moment": "^2.22.1",
     "node-fetch": "^2.1.2",
-    "yargs": "^12.0.1"
+    "yargs": "^15.0.1"
   },
   "bin": {
     "moneyd": "./bin/moneyd.js"