Updated CONTRIBUTING.md with all existing python/robot standards.
Updated CONTRIBUTING.md with all existing python/robot standards.

Change-Id: I19e1c158889a891fe0d0620adb779df58c2a9e51
Signed-off-by: Michael Walsh <10404802c7de463f402c4a18638106ca1b12ef61@us.ibm.com>

openbmc/openbmc-test-automation,openbmc/openbmc-test-automation