BUG: pandas-dev#1982 fix index.summary() to handle unicode in indices

internal representations should be unicode objects, not
strings, conversion should be at I/O contact-points only.

Note: this still does not address the problem of pprinting
indices that have a tuple of unicode strings, as a value.
This issue came up before, monkey-patched in f4e3ab6,
but second time around - a more general solution is needed.

Author: y-p

pandas/core/index.py

@@ -196,7 +196,7 @@ def _has_complex_internals(self):
 
     def summary(self, name=None):
         if len(self) > 0:
-            index_summary = ', %s to %s' % (str(self[0]), str(self[-1]))
+            index_summary = ', %s to %s' % (unicode(self[0]), unicode(self[-1]))
         else:
             index_summary = ''