Add Makefile / .drone.yml, use go module with vendor (#20)

* add Makefile / .drone.yml, use go module with vendor

* Update .drone.yml

Co-Authored-By: lunny <xiaolunwen@gmail.com>

vendor/gopkg.in/src-d/go-git.v4/plumbing/revision.go

@@ -0,0 +1,11 @@
+package plumbing
+
+// Revision represents a git revision
+// to get more details about git revisions
+// please check git manual page :
+// https://www.kernel.org/pub/software/scm/git/docs/gitrevisions.html
+type Revision string
+
+func (r Revision) String() string {
+	return string(r)
+}