fwdpp 0.7.3

• The return value of fwdpp::ts::table_simplifier::simplify has been changed to include a list of indexes to mutations
  that are preserved by simplification. This return value may be passed to a new overload of fwdpp::ts::make_mut_queue
  that avoids tree traversal entirely. This new overload can result in big speedups for simulations where ancestral
  samples are being recorded. However, it only applies for simulations where it is "ok" to keep fixations around.
  PR 167
• fwdpp::sugar::popbase::mcounts_from_preserved_nodes added, mostly out of convenience, so that simulations doing
  tree sequence recording don't have to remember to create the extra variable.
• operator==/!= are now inline for fwdpp::ts::edge, fwdpp::ts::node, fwdpp::ts::mutation_record, and
  fwdpp::ts::table_collection