Some dates cause error when calling dataframe.convert_objects
- Example codes:
  <pre>
  li = [datetime.datetime(3800, 1, 1), ]
  li_df = DataFrame(li)
  li_df.convert_objects()
  </pre>
  then raise the following exception:
  <pre>
  ValueError                                Traceback (most recent call last)
  <ipython-input-112-1cb5a6d822e9> in <module>()
  ----> 1 li_df.convert_objects()
  /usr/local/lib/python2.6/dist-packages/pandas-0.10.1.dev_6e2b6ea-py2.6-linux-x86_64.egg/pandas/core/frame.pyc in convert_objects(self, convert_dates)
  1661         for col, s in self.iteritems():
  1662             if s.dtype == np.object_:
  -> 1663                 new_data[col] = convert_f(s)
  1664             else:
  1665                 new_data[col] = s
  /usr/local/lib/python2.6/dist-packages/pandas-0.10.1.dev_6e2b6ea-py2.6-linux-x86_64.egg/pandas/core/frame.pyc in <lambda>(x)
  1656         new_data = {}
  1657         convert_f = lambda x: lib.maybe_convert_objects(
  -> 1658             x, convert_datetime=convert_dates)
  1659 
  1660         # TODO: could be more efficient taking advantage of the block
  /usr/local/lib/python2.6/dist-packages/pandas-0.10.1.dev_6e2b6ea-py2.6-linux-x86_64.egg/pandas/lib.so in pandas.lib.maybe_convert_objects (pandas/lib.c:33656)()
  /usr/local/lib/python2.6/dist-packages/pandas-0.10.1.dev_6e2b6ea-py2.6-linux-x86_64.egg/pandas/tslib.so in pandas.tslib.convert_to_tsobject (pandas/tslib.c:10796)()
  /usr/local/lib/python2.6/dist-packages/pandas-0.10.1.dev_6e2b6ea-py2.6-linux-x86_64.egg/pandas/tslib.so in pandas.tslib._check_dts_bounds (pandas/tslib.c:11827)()
  ValueError: Out of bounds nanosecond timestamp: 3800-01-01 00:00:00
  </pre>
