issue when read_html with previous fix

With read_html, the fix didn't work on Python 2.7.  Handle the string
conversion correctly

Author: Dr-Irv

pandas/io/parsers.py

@@ -865,9 +865,12 @@ def _extract_multi_indexer_columns(self, header, index_names, col_names,
 
         # extract the columns
         field_count = len(header[0])
+        
+        def tostr(x):
+            return str(x) if not isinstance(x, compat.string_types) else x
 
         def extract(r):
-            return tuple([str(r[i]) for i in range(field_count) if i not in sic])
+            return tuple([tostr(r[i]) for i in range(field_count) if i not in sic])
 
         columns = lzip(*[extract(r) for r in header])
         names = ic + columns