title: pymysql returns wrong values for BIT type
body: <p>I'm using <code>pymysql==0.10.1</code> (python3.7) to read a table with a BIT column, and getting wrong values:</p>
  <pre class="lang-sql prettyprint-override"><code>CREATE TABLE root.numeric
  (BIT_COL       BIT(10));
  insert into root.numeric
  values (b'0010001000');
  insert into root.numeric
  values (b'0000100000');
  </code></pre>
  <p>and then</p>
  <pre class="lang-py prettyprint-override"><code>        with connection.cursor() as cursor:
                  sql = f&quot;select * from `root`.`numeric`;&quot;
                  cursor.execute(sql)
                  result = cursor.fetchone()
                  print(&quot;mysql payload&quot;, result)
  </code></pre>
  <p>getting:</p>
  <pre><code>mysql payload {'BIT_COL': b'\x00\x88'} # nice
  mysql payload {'BIT_COL': b'\x00 '}.   # not nice
  </code></pre>
  <p>why is that? I checked and it looks like the pymysql code isn't converting anything for BIT fields.</p>