Add release notes for 1.0.0-rc4.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>

doc/release-notes/release-notes-1.0.0-rc4.md

@@ -0,0 +1,14 @@
+Daira Hopwood (3):
+      Update pchMessageStart for mainnet and testnet.
+      Update version numbers for 1.0.0-rc4.
+      Add release notes for 1.0.0-rc4.
+
+Jack Grigg (4):
+      Integrate production Founders' Reward keys
+      Remove Founders' Reward override from #1398
+      Regenerate mainnet and testnet genesis blocks for nMaxTipAge change
+      Update tests for new genesis blocks
+
+Sean Bowe (1):
+      Zcash zk-SNARK public parameters for 1.0 "Sprout".
+