stochastic bug in saving dataframes with "int16" or "int32" columns to HDF5 file
There seems to be a strange random bug in saving dataframes with integer columns to HDF5 files. The error sounds like:

```
ValueError: invalid combinate of [values_axes] on appending data [name->values_block_1,cname->values_block_1,axis->None,pos->2,kind->integer] vs current table [name->values_block_1,cname->values_block_1,axis->None,pos->2,kind->integer]
```

and the full traceback:

```
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-13-91a60d72b1ca> in <module>()
     25     print raw.dtypes
     26     store = pd.HDFStore('possible_bug9.h5')
---> 27     store.append('raw', raw)
     28     store.close()

/Users/v/.virtual_envs/system/lib/python2.7/site-packages/pandas/io/pytables.pyc in append(self, key, value, columns, **kwargs)
    608             raise Exception("columns is not a supported keyword in append, try data_columns")
    609 
--> 610         self._write_to_group(key, value, table=True, append=True, **kwargs)
    611 
    612     def append_to_multiple(self, d, value, selector, data_columns=None, axes=None, **kwargs):

/Users/v/.virtual_envs/system/lib/python2.7/site-packages/pandas/io/pytables.pyc in _write_to_group(self, key, value, index, table, append, complib, **kwargs)
    869             raise ValueError('Compression not supported on non-table')
    870 
--> 871         s.write(obj = value, append=append, complib=complib, **kwargs)
    872         if s.is_table and index:
    873             s.create_index(columns = index)

/Users/v/.virtual_envs/system/lib/python2.7/site-packages/pandas/io/pytables.pyc in write(self, obj, axes, append, complib, complevel, fletcher32, min_itemsize, chunksize, expectedrows, **kwargs)
   2738         # create the axes
   2739         self.create_axes(axes=axes, obj=obj, validate=append,
-> 2740                          min_itemsize=min_itemsize, **kwargs)
   2741 
   2742         if not self.is_exists:

/Users/v/.virtual_envs/system/lib/python2.7/site-packages/pandas/io/pytables.pyc in create_axes(self, axes, obj, validate, nan_rep, data_columns, min_itemsize, **kwargs)
   2482         # validate the axes if we have an existing table
   2483         if validate:
-> 2484             self.validate(existing_table)
   2485 
   2486     def process_axes(self, obj, columns=None):

/Users/v/.virtual_envs/system/lib/python2.7/site-packages/pandas/io/pytables.pyc in validate(self, other)
   2096                     oax = ov[i]
   2097                     if sax != oax:
-> 2098                         raise ValueError("invalid combinate of [%s] on appending data [%s] vs current table [%s]" % (c,sax,oax))
   2099 
   2100                 # should never get here

ValueError: invalid combinate of [values_axes] on appending data [name->values_block_1,cname->values_block_1,axis->None,pos->2,kind->integer] vs current table [name->values_block_1,cname->values_block_1,axis->None,pos->2,kind->integer]
```

Interestingly, the error is not deterministic and depends at least on (i) set of other (non-integer) columns in dataframe and (ii) size of dataframe.

Unfortunately I was unable to narrow it down to "just-code" report, so I have to attach a piece of data and an ipython notebook. This is a minimal code in which I was able to reproduce the bug.

https://www.dropbox.com/s/myo03sbqbulzvaj/pandas_possible_bug.zip

the pandas version is 0.11.0, pytables version: 3.0.0
