Change Array to subclass SQLAlchemy's ARRAY

Array previously threw a NotImplementedError for the python_type
attribute and returned True for hashable. After inheriting from
SQLAlchemy's ARRAY type, it returns list and False as expected.

clickhouse_sqlalchemy/types/common.py

@@ -27,13 +27,12 @@ class Boolean(types.Boolean, ClickHouseTypeEngine):
     pass
 
 
-class Array(ClickHouseTypeEngine):
+class Array(types.ARRAY, ClickHouseTypeEngine):
     __visit_name__ = 'array'
 
     def __init__(self, item_type):
-        self.item_type = item_type
         self.item_type_impl = to_instance(item_type)
-        super(Array, self).__init__()
+        super(Array, self).__init__(item_type)
 
     def literal_processor(self, dialect):
         item_processor = self.item_type_impl.literal_processor(dialect)