MGT-python 1.11.1

Changed

• The threshold figure recorded in 1.11.0 is superseded by the full corpus. That release
  quoted a 0.4 % median cost at threshold=0.05, measured on 83 clips. The run finished at 345:
  the cost is 0.2 %, the direction is still consistent and significant at the lower
  thresholds (202 of 345 at the default, sign test p = 0.002), and at threshold=0.2 it stops
  being significant at all (187 of 345, p = 0.13). The conclusion is unchanged and stronger --- the
  picture-legible default is free, for practical purposes, for machine analysis of this material.
  The sequence is recorded in the docstring because it is the useful part: 6 clips said no effect,
  23 said 1.2 %, 83 said 0.4 %, 345 says 0.2 %.