Update configuration file name

The configuration mentions `metacpan_web.conf`, which in fact has become `metacpan_web.yaml`.

Author: ehuelsmann

README.md

@@ -102,11 +102,11 @@ with `precious path/to/file`
 
 The back end defaults to `api.metacpan.org/v1`. Running a local API server is
 optional and not required to hack on the front end. The address to the API being
-used can be changed in the `metacpan_web.conf` file. Ideally you would create a
+used can be changed in the `metacpan_web.yaml` file. Ideally you would create a
 new file called `metacpan_web_local.conf` that contains
 
 ```bash
-api: http://127.0.0.1:5000
+api                 http://127.0.0.1:5000
 ```
 
 which will be loaded on top of the existing config file.