Add discard_url_scheme, discard_url_host, discard_url_port, discard_url_path option

If set to `true`, scheme (use `url_scheme` key) will be added to the record. Defaults to `false`.

If set to `true`, host (use `url_host` key) will be added to the record. Defaults to `false`.

If set to `true`, post (use `url_port` key) will be added to the record. Defaults to `false`.

If set to `true`, path (use `url_path` key) will be added to the record. Defaults to `false`.
Replace `discard_url_(scheme|host|port|path)` to `add_url_(scheme|host|port|path)`
Fix README
Merge pull request #9 from bash0C7/url_scheme_host_port_path_add_to_record

URL scheme, host, port, path add to the record