Merge branch 'master' into docs

docs/source/02-02-advanced-configuration.md

@@ -524,4 +524,11 @@ Sets the logging level for the context logger (from [Bunyan](https://github.com/
 - `warn`
 - `info`
 - `debug`
-- `trace`
+- `trace`
+
+## TALK_SCRAPER_HEADERS
+
+A JSON string representing the configuration passed to the
+[fetch](https://www.npmjs.com/package/node-fetch) call for the scraper. It
+can be used to set an authorization header, or change the user agent. (Default
+`{}`)