add fork description

Author: dsahdr

README.md

@@ -10,6 +10,23 @@ A Python library for interacting with Ethereum.
 
 ---
 
+## Rock'N'Block Fork 
+Added support of multiple rpc nodes for HTTPProvider.
+Usage:
+```
+from web3 import Web3
+
+web3 = Web3(
+    Web3.HTTPProvider(
+        [endpoint1, endpoint2, ...]
+    )
+)
+```
+For a backwards compatibility you can still pass a single string rpc provider as usual, i.e. ```Web3.HTTPProvider('endpoint')```
+
+For any blockchain call using web3 (simple requests like "gas_price", or contract interactions and filters,), web3 instance will try to make a call using one provider at once in cycle, and will change provider if any RequestException is thrown. If all endpoints are invalid, built-in "CannotHandleRequest" Exception is thrown.
+
+
 ## Quickstart
 
 [Get started in 5 minutes](https://web3py.readthedocs.io/en/latest/quickstart.html) or