- Pre-release of version 3.0.
- `--v3` option enables phono3py version 3 behaviour. In phono3py-v3, it is
planned to replace $\sum_{l'l''}\Phi_{\alpha\beta\gamma}(0\kappa, l'\kappa',
l''\kappa'') \cdots$ in Eq.(41) of
<https://journals.jps.jp/doi/10.7566/JPSJ.92.012001> by
$[\sum_{l'l''}\Phi_{\alpha\beta\gamma}(0\kappa, l'\kappa', l''\kappa'') \cdots + \sum_{ll''}\Phi_{\alpha\beta\gamma}(l\kappa, 0\kappa', l''\kappa'') \cdots + \sum_{ll'}\Phi_{\alpha\beta\gamma}(l\kappa, l'\kappa', 0\kappa'') \cdots] / 3$
for better treatment of lattice sum in supercell although this requires more
computational demand. In phono3py-v3, `--v2` option will be prepared.