title: Find rows in dataframe with more than one zero
body: <p>Let's say I have a dataframe like this:
  df = data.frame(c(1:5), c(0,0,3,1,0), c(0,2,0,0,0), c(0,0,7,1,2)</p>
  
  <pre><code>1 0 0 0
  2 0 2 0
  3 3 0 7
  4 1 0 1
  5 0 0 2
  </code></pre>
  
  <p>What should I do so I only get the rows that contain more than one zero? </p>
  
  <pre><code>1 0 0 0
  2 0 2 0
  5 0 0 2
  </code></pre>
  
  <p>Thanks!</p>