CI: split up Cortex-M0 in two groups

.strider.yml

.travis.yml

boards/airfy-beacon/Makefile.features

boards/nrf51dongle/Makefile.features

boards/nrf6310/Makefile.features

boards/nucleo-f091/Makefile.features

boards/pca10000/Makefile.features

boards/pca10005/Makefile.features

boards/saml21-xpro/Makefile.features

boards/samr21-xpro/Makefile.features

boards/stm32f0discovery/Makefile.features

boards/weio/Makefile.features

boards/yunjia-nrf51822/Makefile.features

dist/tools/drone-scripts/build_and_test.sh

dist/tools/travis-scripts/get-pkg-list.py