hydra-evaluator: Do the actual work in a subprocess

This should get rid of the slow memory leaks exhibited by hydra-evaluator.

Created by  Eelco Dolstra  on September 21, 2013
3CVY4QJXRFFA6V4JVBPMSPRKL2KGBCCE3HSOFWVUK76GIGO3NDPAC
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