Support unicode attributes at HDF5 level
Fix comments
PyTables now requires Python 2.6 or newer
Fix calls to the PyString C API.

Replace calls to the PyString_* API with calls to PyBytes_* and
PyUnicode_* as needed.
Fixed char* in function/method signatures

All python function an method that get a char* as parameter have been
fixed so to work alsi with unicode arguments (utf-8 encoding has been
used).
Encode self.name of all node classes in cython extension modules
Use encoded name in _g_get_objinfo
Use encoded name in getFilters
Minor changes
Typo
String type for function args
Fix doctests for python 3
Fixed getslot method in NodeCache
Use open istead of file
Only test str field named in python 3
Decode subprocess output
Encode attribute names in _createTable
Encode field names in createNestedType
Now read_f_attr reads unicode attributes correctly
Make VlenStrAttrTestCase compatible with python 3