title: python pandas read_csv not recognizing \t in tab delimited file
body: <p>I'm trying to read in the following tab separated data into pandas:<br>
  test.txt:  </p>
  
  <pre><code>col_a\tcol_b\tcol_c\tcol_d
  4\t3\t2\t1  
  4\t3\t2\t1 
  </code></pre>
  
  <p>I import test.txt as follows:  </p>
  
  <pre><code>pd.read_csv('test.txt',sep='\t')
  </code></pre>
  
  <p>The resulting dataframe has 1 column.  The \t is not recognized as tab.  </p>
  
  <p>If I replace \t with a 'keyboard tab' the file is parsed correctly. I also tried replacing '\t with \t and /t and didn't have any luck.  </p>
  
  <p>Thanks in advance for your help.<br>
  Omar </p>
  
  <p>PS: Screenshot <a href="https://imgur.com/a/nXvW3" rel="noreferrer">http://imgur.com/a/nXvW3</a></p>