Saving DataFrame with tuple index to HDFStore fails
The following code fails on pandas 0.6.1

```
import numpy as np
import pandas
col = np.arange(10)
idx = [(0.,1.), (2., 3.), (4., 5.)]
data = np.random.randn(30).reshape((3, 10))
DF = pandas.DataFrame(data, index=idx, columns=col)
H = pandas.HDFStore("test.h5", "w")
H['data'] = DF
H.close()
```

The traceback is as follows:

```
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
/home2/hilboll/<ipython-input-15-a313de079f58> in <module>()
----> 1 H['data'] = DF

/home2/hilboll/.virtualenvs/pydoas/lib/python2.7/site-packages/pandas/io/pytables.pyc in __setitem__(self, key, value)
    121 
    122     def __setitem__(self, key, value):
--> 123         self.put(key, value)
    124 
    125     def __len__(self):

/home2/hilboll/.virtualenvs/pydoas/lib/python2.7/site-packages/pandas/io/pytables.pyc in put(self, key, value, table, append, compression)
    259         """
    260         self._write_to_group(key, value, table=table, append=append,
--> 261                              comp=compression)
    262 
    263     def _get_handler(self, op, kind):

/home2/hilboll/.virtualenvs/pydoas/lib/python2.7/site-packages/pandas/io/pytables.pyc in _write_to_group(self, key, value, table, append, comp)
    327             wrapper = lambda value: handler(group, value)
    328 
--> 329         wrapper(value)
    330         group._v_attrs.pandas_type = kind
    331 

/home2/hilboll/.virtualenvs/pydoas/lib/python2.7/site-packages/pandas/io/pytables.pyc in <lambda>(value)
    325 
    326             handler = self._get_handler(op='write', kind=kind)
--> 327             wrapper = lambda value: handler(group, value)
    328 
    329         wrapper(value)

/home2/hilboll/.virtualenvs/pydoas/lib/python2.7/site-packages/pandas/io/pytables.pyc in _write_frame(self, group, df)
    336 
    337     def _write_frame(self, group, df):
--> 338         self._write_block_manager(group, df._data)
    339 
    340     def _read_frame(self, group, where=None):

/home2/hilboll/.virtualenvs/pydoas/lib/python2.7/site-packages/pandas/io/pytables.pyc in _write_block_manager(self, group, data)
    347         group._v_attrs.ndim = data.ndim
    348         for i, ax in enumerate(data.axes):
--> 349             self._write_index(group, 'axis%d' % i, ax)
    350 
    351         # Supporting mixed-type DataFrame objects...nontrivial


/home2/hilboll/.virtualenvs/pydoas/lib/python2.7/site-packages/pandas/io/pytables.pyc in _write_index(self, group, key, index)
    439         else:
    440             setattr(group._v_attrs, '%s_variety' % key, 'regular')
--> 441             converted, kind, _ = _convert_index(index)
    442             self._write_array(group, key, converted)
    443             node = getattr(group, key)

/home2/hilboll/.virtualenvs/pydoas/lib/python2.7/site-packages/pandas/io/pytables.pyc in _convert_index(index)
    734         return np.asarray(values, dtype=np.float64), 'float', atom
    735     else: # pragma: no cover
--> 736         raise ValueError('unrecognized index type %s' % type(values[0]))
    737 
    738 def _read_array(group, key):

ValueError: unrecognized index type <type 'tuple'>
```
