problem: doesn't respond to eth_chainId method

fix: #22

src/test/groovy/io/emeraldpay/dshackle/upstream/calls/DefaultEthereumMethodsSpec.groovy

@@ -0,0 +1,26 @@
+package io.emeraldpay.dshackle.upstream.calls
+
+import io.emeraldpay.grpc.Chain
+import spock.lang.Specification
+
+class DefaultEthereumMethodsSpec extends Specification {
+
+    def "eth_chainId is hardcoded"() {
+        setup:
+        def methods = new DefaultEthereumMethods(Chain.ETHEREUM)
+        when:
+        def act = methods.isHardcoded("eth_chainId")
+        then:
+        act
+    }
+
+    def "Provides hardcoded correct chainId"() {
+        expect:
+        new String(new DefaultEthereumMethods(chain).executeHardcoded("eth_chainId")) == id
+        where:
+        chain                  | id
+        Chain.ETHEREUM         | "0x0"
+        Chain.ETHEREUM_CLASSIC | "0x3d"
+        Chain.TESTNET_KOVAN    | "0x2a"
+    }
+}