Merge pull request #8210 from astralien3000/teensy31

boards/teensy31/Makefile

boards/teensy31/Makefile.dep

boards/teensy31/Makefile.features

boards/teensy31/Makefile.include

boards/teensy31/board.c

boards/teensy31/doc.txt

boards/teensy31/include/board.h

boards/teensy31/include/periph_conf.h

cpu/kinetis/include/cpu_conf_kinetis.h

cpu/kinetis/include/cpu_conf_kinetis_k.h

cpu/kinetis/include/vendor/MK20D7.h

cpu/kinetis/kinetis-info.mk

dist/tools/teensy-loader-cli/.gitignore

dist/tools/teensy-loader-cli/Makefile

dist/tools/teensy-loader-cli/build.sh

tests/unittests/Makefile