vbench is a flexible framework used to benchmark HTTP server
performance.

TODO

* support multiple request dimensions with separate analyze chains.

* log information for different dimensions to different files.

* save failed requests to disk.

* enable/disable keep-alive per request.

* save selected responses to disk.

* support 'real-time' query log replay (need format).

* tag all components in model with unique names.

* support external get/set of selected values.