Attempt to fix issue #10366 encoding and categoricals hdf serialization.
closes #10366 . 

Probably not quite the right approach but want to run travis. Tests are a bit weak at this point (just testing for non-exceptions). Encoding issues might be relevant to other types besides categoricals (but categoricals raise exceptions when strings to mangled to non-uniqueness).

Also, let's make a store in 0.16.2. and try it on the current to see if back-compat can be rescued. (but do this after you have it completely working; you might have to try things to 'detect' the encoding, e.g. try to re-encode in 'utf-8' and some such).
 I haven't resolved the python2 issue (TypeError: [unicode] is not implemented as a table column) so have put a skip in the test for PY2.

In Python 3.4.3, have successfully created a store in 0.16.2 and read it using the current branch.
 @jreback I've squashed. Let me know if there are other comments/concerns. 
 can you rebase / update?
 Rebased and squashed.
 @cottrell can you rebase and update according to my last
 @jreback I have rebased and commented above that I did not get very far with the _convert_string_array suggestion you made.
 ok will take a look thxs
 replaced by #10889 
