v0.2.11

• Add poststratification over posterior samples (closes #21).
• shape() now accepts aggregated item response data unaccompanied by
  individual-level item response data. The item_data and item_names
  arguments are no longer required.
• Add a max_raked_weight argument to shape() for trimming raked weights.
  Note that trimming occurs before raked weights are rescaled to have mean 1,
  and the rescaled weights can be larger than max_raked_weight.
• Remove the unused function expand_rownames().
• Bugfixes.