add github.com/pkg/errors to glide and vendor

This adds github.com/pkg/errors to glide.yaml followed
by glide and glide-vc commands. The github.com/pkg/errors
package is currently required mainly for the errors.Wrap()
and errors.New() methods, since this lets us to annotate the
errors while passing the error message up the call stack.

vendor/github.com/spf13/pflag/ip.go

@@ -6,6 +6,8 @@ import (
 	"strings"
 )
 
+var _ = strings.TrimSpace
+
 // -- net.IP value
 type ipValue net.IP