tree 74ba8da1979c85cc72e1bba240a1799a5044bed2
parent 2c4da27f6c50649dbfb940644bfdaf91638c2a48
author Gunnar Mills <gmills@us.ibm.com> 1572870082 -0600
committer Gunnar Mills <gmills@us.ibm.com> 1573091048 +0000

CONTRIBUTING.md: grammar and strengthen wording

https://app.grammarly.com has a free grammar checker.
It flagged several things in the CONTRIBUTING file, fixed some
them.
Also strengthened the wording around using system() from almost
never to do not use.

Learn something new every day:
https://www.dailywritingtips.com/that-vs-which/

Change-Id: Ic12468761866ee2165b324f0c87245369f79e0d3
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>