Fix missed imports & working dummy_model example

Author: nik

label_studio_ml/__init__.py

@@ -1,5 +1,7 @@
+from .model import LabelStudioMLBase
+
 # Package name
 package_name = 'label-studio-ml'
 
 # Package version
-__version__ = '1.0.0'
+__version__ = '1.0.0'

label_studio_ml/examples/dummy_model.py

@@ -1,6 +1,6 @@
 import random
 
-from label_studio.ml import LabelStudioMLBase
+from label_studio_ml import LabelStudioMLBase
 
 
 class DummyModel(LabelStudioMLBase):