flav-io/flavio v0.24

This is a relatively minor release, but major changes are in the pipeline which also require some future changes in dependencies, please read on below.

• The longitudinal polarization fraction in B→Kνν, `'FL(B0->Knunu)'`
• The branching ratio of the inclusive semi-tauonic decay 'BR(B->Xctaunu)' as well as lepton flavour ratios like 'Rtaul(B->Xclnu)'

• Several typos in the QCD factorization contributions to B→Vll decays spotted by @SatoshiMishima. The numerical impact is small.

This will be the last version of flavio working with Python 3.4. The next version will require at least Python 3.5. Python 3.5 was released in September 2015; the current version is 3.6. If you have a reasonably recent Linux distribution (e.g. Ubuntu 16.04 LTS or newer), you should be fine (you can check your Python version by running python3 --version). If you are on an outdated system and cannot update Python, have a look at conda. It allows you to install the newest version of Python in a virtual environment without root privileges. Conda is also the best choice if you are on Windows.