Add missing Array attributes

[jonburdo]

Array previously threw a NotImplementedError for the python_type attribute and returned True for hashable.

• fixes Array has incorrect attributes #254

Checklist:

• Add tests that demonstrate the correct behavior of the change. Tests should fail without the change.
• Add or update relevant docs, in the docs folder and in code.
• Ensure PR doesn't contain untouched code reformatting: spaces, etc.
• Run flake8 and fix issues.
• Run pytest no tests failed. See https://clickhouse-sqlalchemy.readthedocs.io/en/latest/development.html.

[coveralls]

coverage: 85.736% (+0.4%) from 85.376% when pulling 49ef908 on jonburdo:fix-array-attributes into 800dcfb on xzkostyan:master.