Update __init__.py

Author: bmoscon

arctic/__init__.py

@@ -1,7 +1,7 @@
 """ The Arctic TimeSeries and Tick store."""
 
 from .arctic import Arctic, register_library_type
-from .arctic import VERSION_STORE, TICK_STORE
+from .arctic import VERSION_STORE, TICK_STORE, CHUNK_STORE
 from .store.version_store import register_versioned_storage
 from .store._pandas_ndarray_store import PandasDataFrameStore, PandasSeriesStore, PandasPanelStore
 from .store._ndarray_store import NdarrayStore