Rework negroni Logger creation
Rework negroni Logger creation

From `go vet`:

webhook.go:98: github.com/codegangsta/negroni.Logger composite literal uses unkeyed fields

moorereason/webhook,kevinrodbe/webhook,adnanh/webhook,appneta/webhook,Sanji-IO/webhook,pavlo/webhook,ciarand/webhook,imZack/webhook