vendor: sirupsen/logrus -> Sirupsen/logrus

github.com/docker/docker/pkg/archive requires Sirupsen/logrus.
So let's remove sirupsen/logrus at the moment.

Signed-off-by: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>

vendor/github.com/sirupsen/logrus/doc.go

@@ -1,26 +0,0 @@
-/*
-Package logrus is a structured logger for Go, completely API compatible with the standard library logger.
-
-
-The simplest way to use Logrus is simply the package-level exported logger:
-
-  package main
-
-  import (
-    log "github.com/Sirupsen/logrus"
-  )
-
-  func main() {
-    log.WithFields(log.Fields{
-      "animal": "walrus",
-      "number": 1,
-      "size":   10,
-    }).Info("A walrus appears")
-  }
-
-Output:
-  time="2015-09-07T08:48:33Z" level=info msg="A walrus appears" animal=walrus number=1 size=10
-
-For a full guide visit https://github.com/Sirupsen/logrus
-*/
-package logrus