stopper: move to pkg package

This also adds a package docs for the stopper package.

middleware/jwt/jwt.go

@@ -23,7 +23,7 @@ import (
 
 	"github.com/chihaya/chihaya/bittorrent"
 	"github.com/chihaya/chihaya/middleware"
-	"github.com/chihaya/chihaya/stopper"
+	"github.com/chihaya/chihaya/pkg/stopper"
 )
 
 var (

middleware/middleware.go

@@ -9,7 +9,7 @@ import (
 	log "github.com/Sirupsen/logrus"
 	"github.com/chihaya/chihaya/bittorrent"
 	"github.com/chihaya/chihaya/frontend"
-	"github.com/chihaya/chihaya/stopper"
+	"github.com/chihaya/chihaya/pkg/stopper"
 	"github.com/chihaya/chihaya/storage"
 )
 

pkg/stopper/stopper.go

@@ -1,3 +1,4 @@
+// Package stopper implements a pattern for shutting down a group of processes.
 package stopper
 
 import (

storage/storage.go

@@ -2,7 +2,7 @@ package storage
 
 import (
 	"github.com/chihaya/chihaya/bittorrent"
-	"github.com/chihaya/chihaya/stopper"
+	"github.com/chihaya/chihaya/pkg/stopper"
 )
 
 // ErrResourceDoesNotExist is the error returned by all delete methods in the