Updating server dependancies. Also adding github.com/jaytaylor/html2text and gopkg.in/gomail.v2 (#5748)

vendor/github.com/tylerb/graceful/README.md

@@ -3,6 +3,11 @@ graceful [![GoDoc](https://godoc.org/github.com/tylerb/graceful?status.png)](htt
 
 Graceful is a Go 1.3+ package enabling graceful shutdown of http.Handler servers.
 
+## Using Go 1.8?
+
+If you are using Go 1.8, you may not need to use this library! Consider using `http.Server`'s built-in [Shutdown()](https://golang.org/pkg/net/http/#Server.Shutdown)
+method for graceful shutdowns.
+
 ## Installation
 
 To install, simply execute:

vendor/github.com/tylerb/graceful/graceful.go

@@ -366,6 +366,7 @@ func (srv *Server) manageConnections(add, idle, active, remove chan net.Conn, sh
 		select {
 		case conn := <-add:
 			srv.connections[conn] = struct{}{}
+			srv.idleConnections[conn] = struct{}{} // Newly-added connections are considered idle until they become active.
 		case conn := <-idle:
 			srv.idleConnections[conn] = struct{}{}
 		case conn := <-active: