Release v0.15.0: PySide6 GUI, numpy 2.0 & newer scipy compatibility, …

…drop Python 2/PyQt4

Update setup.py

update travis CI install

Update CHANGELOG.md

Merge pull request #68 from andrewpaulreeves/master

Small fixes for 0.12.1

Merge pull request #60 from soapy/conjugatesDMs

Conjugates DMs

Merge branch 'master' of github.com:soapy/soapy

Merge pull request #30 from ojdf/master

ANN reconstructor changes

Update CHANGELOG.md

Update CHANGELOG.md