Bump v3.1.0 for Flutter WASM.

Thanks for @lelejacko contribution - #412

Author: jumperchen

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 3.1.0
+
+**Bug fix:**
+* [#392](https://github.com/rikulo/socket.io-client-dart/issues/392) [Flutter WASM] No transports available
+* [#404](https://github.com/rikulo/socket.io-client-dart/issues/404) Flutter web socket connection problem on wasm
 ## 3.0.2
 
 **Bug fix:**

pubspec.yaml

@@ -1,6 +1,6 @@
 name: socket_io_client
 description: Dartlang port of socket.io-client for web, flutter, dartvm to use
-version: 3.0.2
+version: 3.1.0
 homepage: https://www.zkoss.org
 repository: https://github.com/rikulo/socket.io-client-dart
 issue_tracker: https://github.com/rikulo/socket.io-client-dart/issues