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/go-sdk/gitea/utils.go

@@ -0,0 +1,23 @@
+// 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 gitea
+
+import (
+	"net/http"
+)
+
+var jsonHeader = http.Header{"content-type": []string{"application/json"}}
+
+func Bool(v bool) *bool {
+	return &v
+}
+
+func String(v string) *string {
+	return &v
+}
+
+func Int64(v int64) *int64 {
+	return &v
+}