Modularized `write_some_streaming_content`.
Split ESL emulator code.
Minor rewrite of the `record_to_url` test.

Note how the first `emit` is now done before the stream is created.
record_to_url now testing for both file and pipe scenari.
Oops, the previous version was mixing up test results on the server side!
Initial test-simple set for `play_from_url`.
re-order so that unlink is always done before catching problems.
play_from_url: revert to simpler handling

As I see it the test is failing because Express is not sending the content back to the client.
I also modified the test to count the size sent, however it appears the client is not getting anything.