Bug fixes
* Issue 2 on GitHub fixed.
API changes/new features:
* :class:`fwdpy11.regions.Sregion` may now model distrubitions of effect sizes on scales other than the effect size itself. A scaling parameter allows the DFE to be functions of N, 2N, 4N, etc. PR 16
* Github issues 7, 8, and 9 resolved. All are relatively minor usability tweaks.
* :func:`fwdpy11.util.change_effect_size` added, allowing the "s" and "h" fields of :class:`fwdpy11.fwdpp_types.Mutation` to be changed. [commit](https://github.com/molpopgen/fwdpy11/commit/ba4841e9407b3d98031801d7eea92b2661871eb2)
* The attributes of :class:`fwdpy11.fwdpp_types.Mutation` are now read-only, addressing Issue 5 on GitHub. [commit](https://github.com/molpopgen/fwdpy11/commit/f376d40788f3d59baa01d1d56b0aa99706560011)
* Trait-to-fitness mapping functions for quantitative trait simulations now take the entire population, rather than just the generation. This allows us to model things like truncation selection, etc. [commit](https://github.com/molpopgen/fwdpy11/commit/fa37cb8f1763bc7f0e64c8620b6bc1ca350fddb9)
Back-end changes
------------------------
* Code base updadted to work with pybind11_ 2.2.0. 19
* :mod:`fwdpy11.model_params` has been refactored, addressing issue 4 on GitHub. The new code base is more idiomatic w.r.to Python's OO methods. [commit](https://github.com/molpopgen/fwdpy11/commit/1b811c33ab394ae4c64a3c8894984f320b870f22)
* Many of the C++-based types can now be pickled, making model parameter objects easier to serialize. Most of the
changes are in [this commit](https://github.com/molpopgen/fwdpy11/commit/d0a3602e71a866f7ff9d355d62953ea00c663c5a). This mostly addresses Issue #3 on GitHub
* Added magic numbers to keep track of compatibility changes to serialization formats.
* __str__ changed to __repr__ for region types [commit](https://github.com/molpopgen/fwdpy11/commit/2df859dd74d3de79d941a1cc21b8712a52bcf9ba)
* fwdpy11.model_params now uses try/except rather than isinstance to check that rates are float-like types.[commit](https://github.com/molpopgen/fwdpy11/commit/37112a60cd8fc74133945e522a47183314bf4085)