how the sort the rows by mean difference. Options are to sort
using the mean difference from matching, stratificaiton, both
individually, or no sorting.
ci.sig.color
the color used for confidence intervals that do not span zero.
plot.overall
whether to plot vertical lines for the overall (non-bootsrapped)
estimate and confidence interval.
plot.bootstrap
whether to plot vertical lines for the bootstrap pooled
estimate and confidence interval.