Update readme

Author: touhonoob

README.md

@@ -1,11 +1,15 @@
 # ethereum_util
 
-Ported from:
+**This project is a work in progress.** 
+
+Porting Ethereum utilities from Javascript to Dart:
 
 - https://github.com/ethjs/ethjs-util/
 - https://github.com/ethereumjs/ethereumjs-util
 - https://github.com/simolus3/web3dart/
 - https://github.com/maxholman/rlp
 - https://github.com/MetaMask/eth-sig-util
 - https://github.com/ethereumjs/ethereumjs-abi
-- https://github.com/ethereumjs/ethereumjs-wallet
+- https://github.com/ethereumjs/ethereumjs-wallet
+
+Check [test](./test) folder for usage.

test/typed_data_test.dart

@@ -6,7 +6,7 @@ import 'package:ethereum_util/src/signature.dart';
 import 'package:ethereum_util/src/typed_data.dart';
 import 'package:test/test.dart';
 
-var typedData = TypedData(
+final TypedData typedData = TypedData(
     types: {
       "EIP712Domain": [
         TypedDataField(name: "name", type: "string"),
@@ -86,4 +86,9 @@ void main() {
   test('normalize an unsupported type throws', () {
     expect(() => normalize({}), throwsArgumentError);
   });
+
+  test('toJson', () {
+    expect(jsonEncode(typedData.toJson()),
+        r'{"types":{"EIP712Domain":[{"name":"name","type":"string"},{"name":"version","type":"string"},{"name":"chainId","type":"uint256"},{"name":"verifyingContract","type":"address"}],"Person":[{"name":"name","type":"string"},{"name":"wallet","type":"address"}],"Mail":[{"name":"from","type":"Person"},{"name":"to","type":"Person"},{"name":"contents","type":"string"}]},"primaryType":"Mail","domain":{"name":"Ether Mail","version":"1","chainId":1,"verifyingContract":"0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"},"message":{"from":{"name":"Cow","wallet":"0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"},"to":{"name":"Bob","wallet":"0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"},"contents":"Hello, Bob!"}}');
+  });
 }