Draft: integration tests

This is a sketch to show my idea for integration tests. Since we discussed using Python's http.server, I felt that it was OK to write the entire test suite in Python instead of sh.

In this, we:

1. Start a background thread with a http.server server running.
2. Shell out to wcurl on every test, with the cwd set to a separate temporary directory.
3. Assert stdout, stderr, files created, etc.
4. Stop the server after all tests are finished.

Let me know what you think :^)