title: materialize not work well with select2
body: <p>I found the document  in  materialize UI framework with select2 .</p>
  
  <p>when I did not add   $("select").selet2();  everything is ok . the page like this:
  <a href="https://i.stack.imgur.com/qeIbh.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qeIbh.png" alt="normal page "></a></p>
  
  <p>when I add .select2() function, the page not work well : </p>
  
  <p>the line under select disappeared .
  <a href="https://i.stack.imgur.com/o0Etx.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/o0Etx.png" alt="enter image description here"></a></p>
  
  <p>I push my code into github , and here is the repository:</p>
  
  <p><a href="https://github.com/SeasonXin/material-select2-issue.git" rel="nofollow noreferrer">https://github.com/SeasonXin/material-select2-issue.git</a></p>
  
  <p>hope somebody's support, very thanks ; </p>