CRAN Version 3.1.5

• Removes prior deprecated functions and arguments
• Fix bugs (#78, #81, #86)
• Introduces redist_mergesplit_parallel()
• Adds rbind() generic for redist_plans objects
• Improves sampling speed for SMC and Merge-split with county constraint
• Adds county split measures.
• Adds population overlap measures for plan comparisons.
• Deprecates redist.smc() in favor of redist_smc() and redist.mergesplit() in favor of redist_mergesplit().