Add a basic set of KorvClient tests

[tryexceptpass]

Using pytest as the test framework, add the basic tests that verify a client instance:

• [ ] Instantiate KorvClient connecting to a local server without errors using newly generated SSH keys.
• [ ] GET responses complete with the proper callback.
• [ ] STORE responses complete with the proper callback and with no callback.
• [ ] UPDATE responses complete with the proper callback and with no callback.
• [ ] DELETE responses complete with the proper callback and with no callback.
• [ ] Connection fails with the incorrect host address or port.
• [ ] Connection fails with the incorrect SSH key.