Ported CLI from commander to yargs because yargs suits our large CLI better and is easier to develop with. Split commands into separate files since the file was getting annoyingly long.

lib/cli/doctor/index.js

@@ -0,0 +1,11 @@
+module.exports.command = 'doctor'
+
+module.exports.describe = 'Diagnose potential issues with your installation.'
+
+module.exports.builder = function(yargs) {
+  return yargs
+}
+
+module.exports.handler = function() {
+  return require('../../util/doctor').run()
+}