title: Missing NERDTree Commands
body: <p>I am relatively new to vim and have an issue with NERDTree that I can't seem to figure out.</p>
  
  <p>I seem to be missing a whole bunch of commands so when I map them to keys, I get the message (for example)</p>
  
  <p>Not an editor command: NERDTreeMapToggleBookmarks</p>
  
  <p>If I run :command I can see all the NERDTree global commands in there (those in section 2.1 of the docs) and these all seem to work but that's it.</p>
  
  <p>I am using NERDTree 4.1.0 which I downloaded fresh from the github repo.
  I suspect I may have either missed a step when setting up the plugin or am missing something in my .vimrc but I am at a bit of a loss.</p>
  
  <p>Anyone have any pointers? Like I say, I am new to vim so it could be something really stupid or obvious!! ;)</p>
  
  <p>Many thanks</p>