tests/README: add automated tests guidelines
tests/README: add automated tests guidelines

kaspar030/RIOT,josephnoir/RIOT,josephnoir/RIOT,basilfx/RIOT,OlegHahm/RIOT,basilfx/RIOT,OlegHahm/RIOT,aeneby/RIOT,RIOT-OS/RIOT,aeneby/RIOT,miri64/RIOT,ant9000/RIOT,kYc0o/RIOT,jasonatran/RIOT,OTAkeys/RIOT,kYc0o/RIOT,x3ro/RIOT,x3ro/RIOT,mtausig/RIOT,mtausig/RIOT,miri64/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,smlng/RIOT,ant9000/RIOT,RIOT-OS/RIOT,ant9000/RIOT,kaspar030/RIOT,toonst/RIOT,jasonatran/RIOT,aeneby/RIOT,miri64/RIOT,smlng/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,smlng/RIOT,OTAkeys/RIOT,authmillenon/RIOT,toonst/RIOT,OlegHahm/RIOT,ant9000/RIOT,authmillenon/RIOT,toonst/RIOT,kaspar030/RIOT,OlegHahm/RIOT,yogo1212/RIOT,aeneby/RIOT,smlng/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,josephnoir/RIOT,OTAkeys/RIOT,authmillenon/RIOT,jasonatran/RIOT,toonst/RIOT,mtausig/RIOT,yogo1212/RIOT,x3ro/RIOT,kaspar030/RIOT,basilfx/RIOT,toonst/RIOT,jasonatran/RIOT,x3ro/RIOT,miri64/RIOT,ant9000/RIOT,kaspar030/RIOT,basilfx/RIOT,jasonatran/RIOT,josephnoir/RIOT,josephnoir/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,basilfx/RIOT,kYc0o/RIOT,mtausig/RIOT,yogo1212/RIOT,x3ro/RIOT,yogo1212/RIOT,miri64/RIOT,kYc0o/RIOT,aeneby/RIOT,smlng/RIOT,authmillenon/RIOT,yogo1212/RIOT,authmillenon/RIOT,mtausig/RIOT