Fix case where parent bounding box contains hole

[nrabinowitz]

This issue came up when comparing old/new output for countries: When the parent bounding box is fully contained by the outer polygon but fully contains a hole, we were still including the parent in the output. The fix is to check whether the bounding box contains a vertex of the hole, and fail fast if it does.

[coveralls]

coverage: 98.824% (+0.002%) from 98.822%
when pulling be92c3b on nrabinowitz:hole-fix
into a61a464 on uber:master.