Merge pull request #39 from jessevdk/issue/38

Run go fmt

Fixes #38.
diff --git a/conn_darwin.go b/conn_darwin.go
index 8114b83..a912501 100644
--- a/conn_darwin.go
+++ b/conn_darwin.go
@@ -1,6 +1,7 @@
 package dbus
 
 import (
+	"errors"
 	"os/exec"
 )