add small note for docker issue

Author: daattali

README.md

@@ -213,6 +213,7 @@ Beautiful Jekyll is meant to be so simple to use that you can do it all within t
     ```
     docker run -p 4000:4000 -v `pwd`:/app mangar/jekyll:1.1 bash -c "bundle install; bundle exec jekyll serve"
     ```
+    Note you may need to add `--host 0.0.0.0` after `bundle exec jekyll serve` to get the site to server correctly.
 4. View your website at <http://localhost:4000>.
 
 Disclaimer: I personally am NOT using local development so I don't know much about running Jekyll locally. If you follow this route, please don't ask me questions because unfortunately I honestly won't be able to help!