Implement md5c function, slower than Golang's implementation

keeping it in repo to make further improvements and also rename

        minio-hash ---> crypto

pkgs/crypto/md5c/md5_test.go

@@ -0,0 +1,23 @@
+package md5c
+
+import (
+	"bytes"
+	"encoding/hex"
+	"testing"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type MySuite struct{}
+
+var _ = Suite(&MySuite{})
+
+func (s *MySuite) TestMd5sum(c *C) {
+	testString := []byte("Test string")
+	expectedHash, _ := hex.DecodeString("0fd3dbec9730101bff92acc820befc34")
+	hash, err := Sum(bytes.NewBuffer(testString))
+	c.Assert(err, IsNil)
+	c.Assert(bytes.Equal(expectedHash, hash), Equals, true)
+}