Added documentation on reverse ordering

Author: alangshur

README.md

@@ -80,6 +80,14 @@ stream = contract.stream_events(
 )
 ```
 
+You may also specify descending order to stream in the reverse direction. For example, to stream two batches of 10 events in reverse order from the latest block:
+
+```python
+stream = contract.stream_events(order='desc')
+stream.next(10)
+stream.next(10)
+```
+
 #### Live Streaming
 
 In order to stream live data, you can specify the `live_stream` parameter. If you use this parameter with a stream iterator, it will continously stream new events as they are added to the blockchain (with a ~3s delay from nodes):
@@ -186,6 +194,14 @@ stream = contract.stream_calls(
 )
 ```
 
+You may also specify descending order to stream in the reverse direction. For example, to stream two batches of 10 calls in reverse order from the latest block:
+
+```python
+stream = contract.stream_calls(order='desc')
+stream.next(10)
+stream.next(10)
+```
+
 #### Call Format
 
 Each call from the stream will be returned as a dictionary with the same structure, containing `target`, `context`, `call_data`, `input_data`, and `output_data` fields. The `target` field contains information about the contract and function that was decoded, while the `context` field contains information about the block, transaction, and trace that the call was made in. The `call_data` field contains the decoded call data, while the `input_data` and `output_data` fields contain the decoded input and output data, respectively.