deleting old/unused south migrations (deprecated in Django 1.7)

gracedb/events/south_migrations/0001_initial.py

gracedb/events/south_migrations/0002_auto__add_tag.py

...ations/0003_auto__del_slot__del_unique_slot_event_name.py

gracedb/events/south_migrations/0004_populate_tags.py

...grations/0005_stage1_rm_ligouser__add_new_foreign_keys.py

...ons/0006_stage2_rm_ligouser__populate_new_foreign_keys.py

...tions/0007_stage3_rm_ligouser__remove_old_foreign_keys.py

gracedb/events/south_migrations/0008_auto__del_user.py

gracedb/events/south_migrations/0009_add_single_inspiral.py

...vents/south_migrations/0010_auto__add_field_eventlog_N.py

gracedb/events/south_migrations/0011_calc_logN.py

...outh_migrations/0012_auto__add_unique_eventlog_event_N.py

gracedb/events/south_migrations/0013_empty_sync_migration.py

gracedb/events/south_migrations/0014_add_grb_event_table.py

gracedb/events/south_migrations/0015_add_tag_ana_comm.py

...ents/south_migrations/0016_change_analyst_comments_tag.py

..._migrations/0017_auto__add_field_eventlog_file_version.py

gracedb/events/south_migrations/0018_add_tag_background.py

...ents/south_migrations/0019_auto__add_field_event_perms.py

...nts/south_migrations/0020_add_perms_on_existing_events.py