title: update the version in package.json without clean git working directory (without a task runner like Gulp)
body: <p>When running a: <code>npm version prepatch</code> I get the error: "Git working directory not clean." And then a list of files that aren't committed yet. </p>
  
  <p>However, I'd like to do this prerelease to test some stuff locally using a private npm registry. Meaning that I don't have to commit the files just yet using Git.</p>
  
  <p>Is it possible to update the version in package.json without clean git working directory?</p>