Add tests to make sure no invalid function names get exported

lib/commands.js

@@ -21,6 +21,9 @@ var changeFunctionName = (function () {
 // that provided a functionality to add new commands to the client
 
 commands.list.forEach(function (command) {
+
+    // Some rare Redis commands use special characters in their command name
+    // Convert those to a underscore to prevent using invalid function names
     var commandName = command.replace(/(?:^([0-9])|[^a-zA-Z0-9_$])/g, '_$1');
 
     // Do not override existing functions