Make sure we only strip username if it the message contains it

lib/index.js

@@ -140,7 +140,9 @@ export default class Bot extends EventEmitter {
 
     update.forEach(res => {
       let text = res.message.text;
-      if (text.startsWith('/')) {
+      const selfUsername = `@${this.info.username}`;
+
+      if (text.startsWith('/') && text.indexOf(selfUsername) > -1) {
         // Commands are sent in /command@thisusername format in groups
         const regex = new RegExp(`(/.*)@${this.info.username}`);
         text = text.replace(regex, '$1');