Added support for mneomnic privkeys

ethutil/mnemonic_test.go

+package ethutil
+
+import (
+	"testing"
+)
+
+func TestMnDecode(t *testing.T) {
+	words := []string{
+		"ink",
+		"balance",
+		"gain",
+		"fear",
+		"happen",
+		"melt",
+		"mom",
+		"surface",
+		"stir",
+		"bottle",
+		"unseen",
+		"expression",
+		"important",
+		"curl",
+		"grant",
+		"fairy",
+		"across",
+		"back",
+		"figure",
+		"breast",
+		"nobody",
+		"scratch",
+		"worry",
+		"yesterday",
+	}
+	encode := "c61d43dc5bb7a4e754d111dae8105b6f25356492df5e50ecb33b858d94f8c338"
+	result := MnemonicDecode(words)
+	if encode != result {
+		t.Error("We expected", encode, "got", result, "instead")
+	}
+}
+func TestMnEncode(t *testing.T) {
+	encode := "c61d43dc5bb7a4e754d111dae8105b6f25356492df5e50ecb33b858d94f8c338"
+	result := []string{
+		"ink",
+		"balance",
+		"gain",
+		"fear",
+		"happen",
+		"melt",
+		"mom",
+		"surface",
+		"stir",
+		"bottle",
+		"unseen",
+		"expression",
+		"important",
+		"curl",
+		"grant",
+		"fairy",
+		"across",
+		"back",
+		"figure",
+		"breast",
+		"nobody",
+		"scratch",
+		"worry",
+		"yesterday",
+	}
+	words := MnemonicEncode(encode)
+	for i, word := range words {
+		if word != result[i] {
+			t.Error("Mnenonic does not match:", words, result)
+		}
+	}
+}