0.6.0, third release candidate

This is a major push towards a stable release! A large number of improvements to default behavior, the C++ back end, documentation, and testing are all included. See either the 0.6.0rc2 Milestone or the Change Log in the manual.

One fun thing to note is that simulations with tree sequence recording now use a lot less memory!

To install:

pip install fwdpy11==0.6.0rc2