Add release notes for v0.2.0a40

Author: carver

docs/release_notes/index.rst

@@ -1,4 +1,11 @@
 Release notes
 =============
 
-TODO: Fill this in with Py-EVM release notes
+0.2.0-alpha.40
+--------------
+
+Released Jan 15, 2019
+
+- `#1717 <https://github.com/ethereum/py-evm/pull/1717>`_: Indefinitely postpone the pending Constantinople release
+- `#1715 <https://github.com/ethereum/py-evm/pull/1715>`_: Remove Eth2 Beacon code, moving to
+  trinity project