Adding README, Platformio support and moving license#1

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dchauran wants to merge 3 commits intolofturj:masterfrom

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Commits on Jul 15, 2020

Add readme, add platformio support, moved GPL to root of repo.
dchauran
committed
Remove TMCStepper from platformio until I submit the TMC Stepper work
dchauran
committed
Renaming GPLto LICENSE.txt to follow github convention
dchauran
committed