rpc, evm: refactor (#588)

* stargate: refactor

* remove evm CLI

* rpc: refactor

* more fixes

* fixes fixes fixes

* changelog

* refactor according to namespaces

* fix

* lint

* remove export logic

* fix rpc test

* godoc

rpc/namespaces/web3/api.go

@@ -0,0 +1,26 @@
+package web3
+
+import (
+	"github.com/cosmos/ethermint/version"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+// PublicWeb3API is the web3_ prefixed set of APIs in the Web3 JSON-RPC spec.
+type PublicWeb3API struct{}
+
+// New creates an instance of the Web3 API.
+func NewAPI() *PublicWeb3API {
+	return &PublicWeb3API{}
+}
+
+// ClientVersion returns the client version in the Web3 user agent format.
+func (PublicWeb3API) ClientVersion() string {
+	return version.ClientVersion()
+}
+
+// Sha3 returns the keccak-256 hash of the passed-in input.
+func (PublicWeb3API) Sha3(input hexutil.Bytes) hexutil.Bytes {
+	return crypto.Keccak256(input)
+}