Implemented Map Stack Item:

1) Added new file map.go, map_test.go
2) Added Map, Hash Method to Item interface
3) Implemented Hash Method for every stack items (Boolean, Array, Int, ...)

pkg/vm/stack/bytearray.go

@@ -3,6 +3,7 @@ package stack
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"math/big"
 	"strconv"
 )
@@ -69,3 +70,14 @@ func reverse(b []byte) []byte {
 
 	return dest
 }
+
+//Value returns the underlying ByteArray's value.
+func (ba *ByteArray) Value() []byte {
+	return ba.val
+}
+
+// Hash overrides the default abstract hash method.
+func (ba *ByteArray) Hash() (string, error) {
+	data := fmt.Sprintf("%T %v", ba, ba.Value())
+	return KeyGenerator([]byte(data))
+}