Fix missing comma in LibEIP712.sol domain schema.

Add `chainId` to constructors for all test contracts deriving from `LibEIP712.sol`

contracts/exchange-libs/contracts/src/LibEIP712.sol

@@ -26,7 +26,7 @@ contract LibEIP712 {
         "EIP712Domain(",
         "string name,",
         "string version,",
-        "uint256 chainId",
+        "uint256 chainId,",
         "address verifyingContract",
         ")"
     ));

contracts/exchange-libs/contracts/test/TestLibs.sol

@@ -19,18 +19,25 @@
 pragma solidity ^0.5.5;
 pragma experimental ABIEncoderV2;
 
+import "../src/LibEIP712.sol";
 import "../src/LibMath.sol";
 import "../src/LibOrder.sol";
 import "../src/LibFillResults.sol";
 import "../src/LibAbiEncoder.sol";
 
 
-contract TestLibs is 
+contract TestLibs is
+    LibEIP712,
     LibMath,
     LibOrder,
     LibFillResults,
     LibAbiEncoder
 {
+    constructor (uint256 chainId)
+        public
+        LibEIP712(chainId)
+    {}
+
     function publicAbiEncodeFillOrder(
         Order memory order,
         uint256 takerAssetFillAmount,