Add a write into file example (ClickHouse#437)

examples/write_into_file.py

@@ -0,0 +1,10 @@
+import clickhouse_connect
+
+if __name__ == '__main__':
+    client = clickhouse_connect.get_client()
+    query = 'SELECT number, toString(number) AS number_as_str FROM system.numbers LIMIT 5'
+    fmt = 'CSVWithNames'  # or any other format, see https://clickhouse.com/docs/en/interfaces/formats
+    stream = client.raw_stream(query=query, fmt=fmt)
+    with open("output.csv", "wb") as f:
+        for chunk in stream:
+            f.write(chunk)