Set x-www-form-urlencoded content-type for non-binary data

Set the add_content_type when adding non-binary data with the "-d" and
"--data" options so that a "Content-Type:
application/x-www-form-urlencoded" header will get added to the
request.

wuzz.go

@@ -1030,6 +1030,7 @@ func (a *App) ParseArgs(g *gocui.Gui, args []string) error {
 			data := args[arg_index]
 			if !set_binary_data {
 				data, _ = url.QueryUnescape(data)
+				add_content_type = true
 			}
 			vdata, _ := g.View(REQUEST_DATA_VIEW)
 			setViewTextAndCursor(vdata, data)