crypto: move merkle tree into the hash package

It's all about hashes, so it makes sense putting it there.

pkg/core/block.go

@@ -5,7 +5,7 @@ import (
 	"fmt"
 
 	"github.com/CityOfZion/neo-go/pkg/core/transaction"
-	"github.com/CityOfZion/neo-go/pkg/crypto"
+	"github.com/CityOfZion/neo-go/pkg/crypto/hash"
 	"github.com/CityOfZion/neo-go/pkg/io"
 	"github.com/CityOfZion/neo-go/pkg/util"
 	"github.com/Workiva/go-datastructures/queue"
@@ -30,13 +30,13 @@ func (b *Block) Header() *Header {
 	}
 }
 
-func merkleTreeFromTransactions(txes []*transaction.Transaction) (*crypto.MerkleTree, error) {
+func merkleTreeFromTransactions(txes []*transaction.Transaction) (*hash.MerkleTree, error) {
 	hashes := make([]util.Uint256, len(txes))
 	for i, tx := range txes {
 		hashes[i] = tx.Hash()
 	}
 
-	return crypto.NewMerkleTree(hashes)
+	return hash.NewMerkleTree(hashes)
 }
 
 // rebuildMerkleRoot rebuilds the merkleroot of the block.

pkg/crypto/hash/merkle_tree.go

@@ -1,9 +1,8 @@
-package crypto
+package hash
 
 import (
 	"errors"
 
-	"github.com/CityOfZion/neo-go/pkg/crypto/hash"
 	"github.com/CityOfZion/neo-go/pkg/util"
 )
 
@@ -66,7 +65,7 @@ func buildMerkleTree(leaves []*MerkleTreeNode) (*MerkleTreeNode, error) {
 		b1 := parents[i].leftChild.hash.BytesBE()
 		b2 := parents[i].rightChild.hash.BytesBE()
 		b1 = append(b1, b2...)
-		parents[i].hash = hash.DoubleSha256(b1)
+		parents[i].hash = DoubleSha256(b1)
 	}
 
 	return buildMerkleTree(parents)

pkg/crypto/hash/merkle_tree_test.go

@@ -1,4 +1,4 @@
-package crypto
+package hash
 
 import (
 	"testing"