BUG: ensure Series.name is hashable, #12610 
- [x] closes #12610
- [x] tests added / passed
- [x] passes `git diff upstream/master | flake8 --diff`

pandas >= 0.18.0 will no longer support compatibility with Python version 2.6 and since Python 2.6 we can use the abstract base class collections.Hashable.
