BUG: when reading an HDF5 file with an encoding, default to using this encoding
http://stackoverflow.com/questions/32553207/values-missing-when-loaded-from-pandas-hdf5-file/32587108?noredirect=1#comment53034458_32587108

e.g.

if I 

```
df.to_hdf('foo.h5','df',encoding='utf-8')
```

then

```
pd.read_hdf('foo.h5','df')
```

should pick up the encoding for each table (unless the user overrides by passing in `encoding=...`
