Revert "make commands a global"

This reverts commit 9c2d902c39.

commands.js

@@ -1,6 +1,6 @@
 const fs = require('fs');
 
-global.commands = module.exports = {};
+const commands = module.exports = {};
 
 // Compute the edit distance between the two given strings
 function getEditDistance(sourceString, targetString) {