hawk
switch to github actions, kill travis
Correct me if I'm wrong, but I think make test has been failing since version 1.12 , dated 2016-02-23. Since then tests have been failing for different reasons as seen here per each tag https://github.com/andreineculau/lux/actions
This PR is in fact the same setup as used in https://github.com/for-GET/katt and https://github.com/for-GET/jesse , based on the official OTP Docker images. A pre-step is needed to get git 2.18, because actions/checkout@v2 behaves differently otherwise - complete info is here https://github.com/erlang/docker-erlang-otp/issues/351 .
Since the tests are red, I have disabled the OTP matrix, except for the latest OTP version, in order to save resources. When tests are green, one can git revert --no-edit 6f2c3ba to enable the matrix again. Similarly, one could/should enable LUX_MISC to run doc&misc tests in CI.
