Update import paths from github.com/go-gitea to code.gitea.io (#135)

- Update import paths from github.com/go-gitea to code.gitea.io
- Fix import path for travis

See https://docs.travis-ci.com/user/languages/go#Go-Import-Path

vendor/code.gitea.io/git/commit_archive.go

@@ -0,0 +1,33 @@
+// Copyright 2015 The Gogs Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package git
+
+import (
+	"fmt"
+	"path/filepath"
+	"strings"
+)
+
+type ArchiveType int
+
+const (
+	ZIP ArchiveType = iota + 1
+	TARGZ
+)
+
+func (c *Commit) CreateArchive(target string, archiveType ArchiveType) error {
+	var format string
+	switch archiveType {
+	case ZIP:
+		format = "zip"
+	case TARGZ:
+		format = "tar.gz"
+	default:
+		return fmt.Errorf("unknown format: %v", archiveType)
+	}
+
+	_, err := NewCommand("archive", "--prefix="+filepath.Base(strings.TrimSuffix(c.repo.Path, ".git"))+"/", "--format="+format, "-o", target, c.ID.String()).RunInDir(c.repo.Path)
+	return err
+}