title: StringIO and pandas read_csv
body: <p>I'm trying to mix StringIO and BytesIO with pandas and struggling with some basic stuff.  For example, I can't get "output" below to work, whereas "output2" below does work.  But "output" is closer to the real world example I'm trying to do.  The way in "output2" is from an old pandas example but not really a useful way for me to do it.</p>
  
  <pre><code>import io   # note for python 3 only
              # in python2 need to import StringIO
  
  output = io.StringIO()
  output.write('x,y\n')
  output.write('1,2\n')
  
  output2 = io.StringIO("""x,y
  1,2
  """)
  </code></pre>
  
  <p>They seem to be the same in terms of type and contents:</p>
  
  <pre><code>type(output) == type(output2)
  Out[159]: True
  
  output.getvalue() == output2.getvalue()
  Out[160]: True
  </code></pre>
  
  <p>But no, not the same:</p>
  
  <pre><code>output == output2
  Out[161]: False
  </code></pre>
  
  <p>More to the point of the problem I'm trying to solve:</p>
  
  <pre><code>pd.read_csv(output)   # ValueError: No columns to parse from file
  pd.read_csv(output2)  # works fine, same as reading from a file
  </code></pre>