Doc: update alphanet changelog

docs/introduction/alphanet_changes.rst

@@ -1,11 +1,29 @@
 Changelog
 ---------
 
-For the next reset
-~~~~~~~~~~~~~~~~~~
+Reset 2018-05-03
+~~~~~~~~~~~~~~~~
 
 [Alpha]
 
+- New faucet : https://faucet.tzalpha.net
+
+- `secp256k1` as an alternative to `ed25519`
+
+- 32 endorsers per blocks (was 15)
+
+- Delegation rights are now frozen 5 cycles in advance (approx 15 days
+  in mainnet or 10 hours on zeronet);
+
+- Security deposits are recovered after 5 cycles;
+
+- Rewards and fees are earned after 5 cycles;
+
+- Pending deposits and fees count in the staking balance of a delegate;
+
+- Delegates will be tagged as "deactivated" after 5 cycles of
+  inactivity and they will lose their baking rights;
+
 - Do not allow revealing the same endorsement twice.
 
 - Tez values now have 6 decimals instead of two. The syntax used by
@@ -35,6 +53,13 @@ For the next reset
 
 - Split the code base into separate OPAM packages.
 
+Patch 2018-01-15
+~~~~~~~~~~~~~~~~
+
+[Node]
+
+- Fix a performance issue in block locator computation
+
 
 Reset 2017-11-20
 ~~~~~~~~~~~~~~~~