Update building stuff

- Add a Makefile with common targets (binary, test, validate, ..)
- Use docker to build it (isolated)

And update circleci to work with the new Makefile..

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

traefik.go

@@ -3,6 +3,7 @@ package main
 import (
 	"github.com/BurntSushi/toml"
 	"github.com/codegangsta/negroni"
+	"github.com/emilevauge/traefik/middlewares"
 	"github.com/gorilla/mux"
 	"github.com/mailgun/oxy/forward"
 	"github.com/mailgun/oxy/roundrobin"
@@ -11,7 +12,6 @@ import (
 	"github.com/tylerb/graceful"
 	"github.com/unrolled/render"
 	"gopkg.in/alecthomas/kingpin.v2"
-	"./middlewares"
 	"net/http"
 	"net/url"
 	"os"