Poseidon Sponge Hash with different frame sizes (#52)

* Poseidon Sponge Hash with different frame sizes
* Update deps. Bump go version
* Update & fix linter.
* Refactor a bit.
* Reduce gc pressure

keccak256/keccac256_test.go

@@ -0,0 +1,21 @@
+package keccak256
+
+import (
+	"encoding/hex"
+	"math/big"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestKeccak256(t *testing.T) {
+	const SEED = "mimc"
+	res := Hash([]byte(SEED))
+	assert.Equal(t,
+		"b6e489e6b37224a50bebfddbe7d89fa8fdcaa84304a70bd13f79b5d9f7951e9e",
+		hex.EncodeToString(res))
+	c := new(big.Int).SetBytes(Hash([]byte(SEED)))
+	assert.Equal(t,
+		"82724731331859054037315113496710413141112897654334566532528783843265082629790",
+		c.String())
+}