lyra.py: Simplified code to create artificat_status dictionary.  No
change in functionality.

test_lyra.py: Now have working tests for get_lytaf_events() and
remove_lyra_artifacts().  Relies on a couple local paths though.
Changed name of get_lytaf_events() to extract_lytaf_events() and
reintroduced original get_lytaf_events() function which was
mistakenly deleted earlier in commit history.
Deprecated get_lytaf_events() and altered split_series_using_lytaf()
to use output of extract_lytaf_events() rather than get_lytaf_events().
Made some aesthetic changes suggested by pylint.