Append pd.Series in HDF5 files
I tried to google to see if it supposed to be implemented or not, but did not find anything.

The `append` function does not work for `pd.Series` object. For instance, the following code:

```
ss = pd.Series([1,2,3,4,5])
h5store = pd.HDFStore('tmpstore.h5')
h5store.append('ss',ss)
h5store.close()
```

fails with the error:

```
TypeError: cannot properly create the storer for: [group->ss,value-><class 'pandas.core.series.Series'>]
```

However storing the series like this:

```
store['ss']=ss
```

or appending DataFrames works well.

My version of pandas: 0.11.0, pytables: 3.0.0
