Update __main__.py

delete "." in line 3
from .swmmio import Model -> from swmmio import Model
resolve the error: "from swmmio.swmmio import Model, no module named swmmio" balabala......

swmmio/__main__.py

@@ -1,6 +1,6 @@
 from .run_models.run import run_simple, run_hot_start_sequence
 from .run_models import start_pool
-from .swmmio import Model
+from swmmio import Model
 from itertools import chain
 import os
 import argparse