Add reference to the Makefile-example in README.md
Add OBJDIR reference

Signed-off-by: tinyladi <ladislas@weareleka.com>
Beautify arduino-mk-vars.md

Clean up markdown and add code blocks where needed
Update HISTORY.md with improvements.

Signed-off-by: tinyladi <ladislas@weareleka.com>
Merge branch 'update from sudar'
Update from Sudar/master
Update from Sudar/master
Merge branch 'master' of https://github.com/sudar/Arduino-Makefile into update
Merge branch 'update'
Merge branch 'master' of https://github.com/sudar/Arduino-Makefile into update
Merge branch 'update'
Merge branch 'master' into test