Adds hash_test code

hash.go

@@ -0,0 +1,35 @@
+package go_colorhash
+
+import (
+	"crypto/md5"
+	"encoding/binary"
+	"io"
+)
+
+const MaxUint = ^uint(0)
+const MaxInt = int(MaxUint >> 1)
+
+func HashString(s string) int {
+	h := md5.New()
+	io.WriteString(h, s)
+	hashb := h.Sum(nil)
+	hashb = hashb[len(hashb)-8:]
+	lsb := binary.BigEndian.Uint64(hashb)
+	sint := int(lsb)
+	if sint < 0 {
+		sint = sint + MaxInt
+	}
+	return sint
+}
+func HashBytes(r io.Reader) int {
+	h := md5.New()
+	io.Copy(h, r)
+	hashb := h.Sum(nil)
+	hashb = hashb[len(hashb)-8:]
+	lsb := binary.BigEndian.Uint64(hashb)
+	sint := int(lsb)
+	if sint < 0 {
+		sint = sint + MaxInt
+	}
+	return sint
+}