- just pass `-include ${cfg}` to the compiler instead of a
temporary custom.h. also do `-DDEVICE=...` and `-DMANUFACTURER=...`
- rework test_build to print using `logging` module
- report leftover configurations, after the failed one exits
- prettify the output and highlight relevant info instead of the whole lines
- remove .travis.yml
- ./travis_{script,install}.sh -> ./ci_{script,install}.sh
- flush stdout in test script to see logs more promptly
- adjust git config to ignore 'detachedHead' warnings
- general conversion from .ino modules into a separate .cpp files
- clean-up internal headers, place libraries into .h. guard .cpp with _SUPPORT flags
- fix some instances of shared variables instead of public methods
- tweak build system to still build a single source file via os environment variable ESPURNA_BUILD_SINGLE_SOURCE
