Add 'make install' script

Makefile

@@ -3,3 +3,6 @@ VERSION=$(shell git describe)-$(shell date -u +%Y%m%d.%H%M%S)
 
 gitlab-git-http-server: main.go
 	go build -ldflags "-X main.Version ${VERSION}" -o gitlab-git-http-server main.go
+
+install: gitlab-git-http-server
+	install gitlab-git-http-server ${PREFIX}/bin/

README.md

@@ -10,6 +10,11 @@ auth request to GitLab Rails app) -> git-upload-pack
 There are two patches in the repo that show what would need to
 change in GitLab / NGINX to make this work.
 
+## Installation
+
+To install into `/usr/local/bin` run `make install`. To install
+into `/foo/bin` run `make install PREFIX=/foo`.
+
 ## Try it out
 
 You can try out the Git server without authentication as follows: