title: Remove duplicate considering a couple of attributes in Pandas
body: <p>I would like to exclude those instances that have the same title and the same year. </p>
  
  <pre><code>     title      votes  ranking  year
  0    Wonderland  19      7.9    1931
  1    Wonderland  120     7.1    1997
  2    Wonderland  3524    7.2    1999
  3    Wonderland  18169   6.6    2003
  4    Wonderland  17      8.7    2010
  5    Wonderland  6       8.5    2012
  6    Wonderland  8       7.4    2012 
  </code></pre>
  
  <p>For example, in this case. I would only remove 5 or 6</p>