Command: add guildOnly flag

src/lib/command.js

@@ -4,6 +4,7 @@ class Command {
     this.aliases = [];
     this.helpText = "No description provided.";
     this.category = "unsorted";
+    this.guildOnly = false;
   }
 
   addAlias(alias) {

src/lib/commandDispatcher.js

@@ -37,6 +37,10 @@ async function runCommand(msg, cmd, line, args) {
     return "No\n\nSent from my iPhone.";
   }
 
+  if (cmdObj.guildOnly && !msg.channel.guild) {
+    return "This command can only be used in guilds.";
+  }
+
   try {
     const ret = cmdObj.callback(msg, line, ...args);
     if (ret instanceof Promise) {