Enhancement: document how to change network port & concurrency factor via YAML

[danxmoran]

The README suggests changing the ports that solvers run on / the number of questions sent to a solver in parallel by modifying Evaluator.scala and Evaluation.scala. It'd be better to show how to tweak these values in per-project YAML config. The base project could then be set up to pull these values from app config rather than have magic numbers floating around.