fwdpp: fwdpp 0.3.6

This release has two changes:

• The lookup tables used internally have been further refined. The result is big speedups for simulations with selection. We've seen run-time speeds improved by as little as 20% and by as much as 20x, depending on the specifics of what is being simulated.

• KTfwd::site_dependent_fitness has been modified to address a bug that would allow fitness to be < 0. No simulation results are affected by this bug because the GNU Scientific Library would have exited with an error when constructing lookup tables with fitnesses < 0, and hence the simulation would not have finished.