Fixed broken unit test test_config.py and test_naive_completion.py

[geleems]

Fixed broken unit test test_config.py and test_naive_completion.py

• test test_config.py was using wrong API for creating temporary directory.
• test_naive_completion.py: these tests were using wrong expected values and wrong API for creating set from completer.get_completions() method
  • test_empty_string_completion
  • test_select_keyword_completion
  • test_function_name_completion
  • test_column_name_completion
  • test_paths_completion
  • test_alter_well_known_keywords_completion

[pensivebrian]

Please make sure these tests pass running with Python 2.7

[geleems]

I found there is 1 test failure in test_naive_completion.py when I ran with Python 2.7. It turned out there is a bug in MssqlCompleter.find_matches() method. When Python 2, the method trys to create Completion object with ASCII string where only unicode string is accepted. All strings in Python 3 are unicode, so it was not blown up on Python 3.