title: Prevent insert mode in vim
body: <p>I often like to have a copy of the file that I am working on open on a second monitor, usually to assist with writing tests. I sometimes mindlessly attempt to edit it on this monitor, rather than the most up to date one. To prevent this, I have been setting read only mode with <code>:set ro</code> but that doesn't prevent me from making changes, it only prevents me from saving. </p>
  
  <p>I would like a lock that turns off the ability to go into insert mode. I could create a toggle that remaps all the insert mode keys, but I was wondering if there is a better solution?</p>