title: Running npm scripts conditionally
body: <p>I have 2 main build configurations - dev and prod. 
  I push updates to a heroku server that run npm install --production to install my app.
  In the package.json I have the following segment:</p>
  
  <pre><code>"scripts": {
      "postinstall": "make install"
  }
  </code></pre>
  
  <p>that runs a make file that is responsible for uglifying the code and some other minor things.</p>
  
  <p>However, I don't need to run this makefile in development mode. Is there any way to conditionally run scripts with npm?.. </p>
  
  <p>Thanks!</p>