Do not use xmlns prefix as the filename for generated files

We already have directory name (=module name) equal to the xmlns prefix.

Having consistency of the filename (all being named models.go) will allow
projects with multiple modules to have somewhat consistent naming within the
directories.

pkg/template/template.go

@@ -26,7 +26,7 @@ func GenerateTypes(schema *xsd.Schema, outputDir string) error {
 	if err != nil {
 		return err
 	}
-	f, err := os.Create(fmt.Sprintf("%s/%s.go", dir, packageName))
+	f, err := os.Create(fmt.Sprintf("%s/models.go", dir))
 	if err != nil {
 		return err
 	}