resolve aanet -> offline

km3io/__init__.py

 from .__version__ import version
 __version__ = version
 
-from .aanet import OfflineReader
+from .offline import OfflineReader
 from .daq import DAQReader

tests/test_aanet.py → tests/test_offline.py

 import unittest
 from pathlib import Path
 
-from km3io.aanet import Reader, OfflineEvents, OfflineHits, OfflineTracks
+from km3io.offline import Reader, OfflineEvents, OfflineHits, OfflineTracks
 from km3io import OfflineReader
 
 SAMPLES_DIR = Path(__file__).parent / 'samples'