Example for custom file name #59

In the readme you say The file name is a timestamp, but feel free to rename it to something more rescriptive.

However, I don't see where this is possible. I'm trying to use this within mocha tests and would like to explicitly set the filename so that I have control of the fixture content in a CI environment to use scrubbed data. The tests do not use request, however, the library that is under test wraps up request as needed by the library.