update release notes and set version number to 3.0

RELEASE-NOTES

@@ -1,5 +1,33 @@
-# Release 2.10
-  * migration to Python3
+# Release 3.0
+
+  * The project was migrated to Python3.
+
+  * Segwit support:
+    - P2SH-segwit scripts are supported and can be used with hardware
+      wallets. To create a segwit wallet, trezor/ledger users will
+      need to provide a BIP49 derivation path.
+    - Native segwit scripts are supported with Electrum software
+      wallets, using a new type of seed. Segwit seeds have version
+      0x100.
+    - Native segwit scripts are represented using bech32 addresses,
+      following BIP173. Note that BIP173 is still in Draft status. If
+      BIP173 is substantially modified or rejected, bech32 wallets may
+      have to be restored from seed. This will not affect funds sent
+      to bech32 addresses, and it will not affect the capacity of
+      Electrum to spend these funds.
+    - By default, the wizard will not create Segwit seeds; users must
+      opt-in with the segwit option.
+    - The BIP32 master keys of segwit wallets are serialized using new
+      version numbers. Version numbers are user visible, with the
+      following prefixes:
+         * xpub/xprv : non-segwit wallet
+         * ypub/yprv : segwit-p2sh wallet
+         * zpub/zprv : native segwit wallet
+
+  * A new version of the Electrum protocol is required by the client
+    (version 1.1). Servers using older versions of the protocol will
+    not be visible in the GUI.
+
 
 # Release 2.9.3
   * fix configuration file issue #2719

lib/version.py

@@ -1,4 +1,4 @@
-ELECTRUM_VERSION = '2.10.0'  # version of the client package
+ELECTRUM_VERSION = '3.0'     # version of the client package
 PROTOCOL_VERSION = '1.1'     # protocol version requested
 
 # The hash of the mnemonic seed must begin with this