title: r dplyr ends_with multiple string matches
body: <p>Can I use dplyr::select(ends_with) to select column names that fit any of multiple conditions. Considering my column names, I want to use ends with instead of contains or matches, because the strings I want to select are relevant at the end of the column name, but may also appear in the middle in others. For instance, </p>
  
  <pre><code>df &lt;- data.frame(a10 = 1:4,
               a11 = 5:8,
               a20 = 1:4,
               a12 = 5:8)
  </code></pre>
  
  <p>I want to select columns that end with 1 or 2, to have only columns a11 and a12. Is select(ends_with) the best way to do this?</p>
  
  <p>Thanks!</p>