Revisit the proposal to use github PR

[jay.zhu...@yahoo.com.INVALID]

It was discussed 1 year's ago: 
https://www.mail-archive.com/dev@cassandra.apache.org/msg11810.html
As all Apache projects are moving to gitbox: 
https://reference.apache.org/committer/github, should we revisit that and 
change our review/commit process to use github PR?A good example is 
Spark:"Changes to Spark source code are proposed, reviewed and committed via 
Github pull requests" (https://spark.apache.org/contributing.html).
/jay