Adds better test data to the test file.

- Fixes tests accordingly.
- Adds a failing test for the clear irrelevant labels feature (TDD).
Adds another test for clear_irrelevant_labels.

- Moves the other test to it's appropriate home.
Clears irrelevant labels after first character.

- This is useful so as to home in on target and for clarification.
- Updates CHANGELOG.md.
- Closes #19.