Roentgen

------------------
* Fix and improvement to gui
* General improvements to documentation and examples
* Removed poetry
* added pre-commit support and updated testing

------------------
* Improvement to documentation to illustrate custom materials
* Added tutorial and documentation to illustrate interpolation
* Going outside of data range (1 keV to 2 MeV) now provides a ValueError instead of failing quietly and filling in zeros for extrapolated values.

------------------
* The Material class can now represent substances with multiple and arbitrary constitutients
* Moved to poetry for dependency management and packaging
* Automated testing now also using poetry
* Added data source information into the documentation
* Updated dependencies versions
* Added a Code of Conduct
* If material (element or compounds) are not found, raises a ValueError instead of returning None
* Increased test coverage
* Added attenuator section to guide.

------------------
* First stable release
* Added gui, deployed to heroku
* Added data and support for emission lines
* Added Response class
* Major update to documentation and moved to sunpy doc theme

------------------
* First release