I refactored `AnnotateRoutes.routes_exists?` and methods using this.
The points are as follows.

*   Removing `puts` in `AnnotateRoutes.routes_exists?`
*   Using `File.exist?` instead of `File.exists?` because `File.exists?` is deprecated
*   Renaming `AnnotateRoutes.routes_exists?` to `AnnotateRoutes.routes_file_exists?` in order to make the name of method more explanatory