* introduce doctest over googletest #202
* call dtester in in targets
* doctest conversion #202
* channel.cpp -> doctest #202
* egcpool tests -> doctest #202
* input tests to doctester
* zaxis -> doctest
* drone: always define LANG
* libav to doctest #202
* panelreel tests to doctest #202
* spec that a C++17 compiler is now required for doctest #202
* enmetric tests -> doctest #202
* fade tests -> doctest #202
* notcurses test case -> doctest #202
* last conversion to doctest #202
* finish move to doctest #202
* drone: set up make test
* planereels tester #180
* suppress_banner in all tests
* tabletcb: start passing back tablet
* properly initialize fbbytes stat
* panelreel: logic fixes#178
* install all testing data
* improved alpha macros
* demo: use new alpha macros
* add ncplane_set_*_alpha()
* explicitly set fg for uniblock
* outro: background is a space #139
* distinct alpha channels for fg/bg #139
* rename 'background' cell to 'default' #142
* doc palette fades