Update contrib/README.
Update contrib/README.

rvs/gpdb,greenplum-db/gpdb,janebeckman/gpdb,Postgres-XL/Postgres-XL,Quikling/gpdb,rvs/gpdb,pavanvd/postgres-xl,cjcjameson/gpdb,postmind-net/postgres-xl,foyzur/gpdb,adam8157/gpdb,xuegang/gpdb,tangp3/gpdb,50wu/gpdb,arcivanov/postgres-xl,techdragon/Postgres-XL,oberstet/postgres-xl,CraigHarris/gpdb,0x0FFF/gpdb,rubikloud/gpdb,50wu/gpdb,yuanzhao/gpdb,randomtask1155/gpdb,CraigHarris/gpdb,yuanzhao/gpdb,kmjungersen/PostgresXL,zaksoup/gpdb,ashwinstar/gpdb,Chibin/gpdb,cjcjameson/gpdb,lisakowen/gpdb,kaknikhil/gpdb,pavanvd/postgres-xl,lisakowen/gpdb,rubikloud/gpdb,zaksoup/gpdb,xuegang/gpdb,ovr/postgres-xl,rubikloud/gpdb,rubikloud/gpdb,Chibin/gpdb,cjcjameson/gpdb,tpostgres-projects/tPostgres,50wu/gpdb,lisakowen/gpdb,janebeckman/gpdb,jmcatamney/gpdb,snaga/postgres-xl,yazun/postgres-xl,chrishajas/gpdb,zeroae/postgres-xl,jmcatamney/gpdb,ahachete/gpdb,Postgres-XL/Postgres-XL,atris/gpdb,snaga/postgres-xl,kmjungersen/PostgresXL,yuanzhao/gpdb,randomtask1155/gpdb,ashwinstar/gpdb,zaksoup/gpdb,tangp3/gpdb,cjcjameson/gpdb,lisakowen/gpdb,ashwinstar/gpdb,chrishajas/gpdb,lpetrov-pivotal/gpdb,kaknikhil/gpdb,edespino/gpdb,tpostgres-projects/tPostgres,greenplum-db/gpdb,yazun/postgres-xl,chrishajas/gpdb,chrishajas/gpdb,rvs/gpdb,edespino/gpdb,kaknikhil/gpdb,lintzc/gpdb,randomtask1155/gpdb,kmjungersen/PostgresXL,50wu/gpdb,CraigHarris/gpdb,0x0FFF/gpdb,tangp3/gpdb,Quikling/gpdb,CraigHarris/gpdb,randomtask1155/gpdb,postmind-net/postgres-xl,rvs/gpdb,lintzc/gpdb,lpetrov-pivotal/gpdb,pavanvd/postgres-xl,tpostgres-projects/tPostgres,greenplum-db/gpdb,janebeckman/gpdb,xuegang/gpdb,rvs/gpdb,edespino/gpdb,xinzweb/gpdb,foyzur/gpdb,0x0FFF/gpdb,lintzc/gpdb,rubikloud/gpdb,chrishajas/gpdb,cjcjameson/gpdb,lpetrov-pivotal/gpdb,edespino/gpdb,xinzweb/gpdb,ashwinstar/gpdb,Postgres-XL/Postgres-XL,adam8157/gpdb,kaknikhil/gpdb,cjcjameson/gpdb,postmind-net/postgres-xl,Postgres-XL/Postgres-XL,cjcjameson/gpdb,ahachete/gpdb,Postgres-XL/Postgres-XL,pavanvd/postgres-xl,edespino/gpdb,xuegang/gpdb,atris/gpdb,kaknikhil/gpdb,kaknikhil/gpdb,royc1/gpdb,oberstet/postgres-xl,janebeckman/gpdb,tangp3/gpdb,Chibin/gpdb,xinzweb/gpdb,ahachete/gpdb,ovr/postgres-xl,lisakowen/gpdb,Quikling/gpdb,rvs/gpdb,lisakowen/gpdb,xinzweb/gpdb,chrishajas/gpdb,Quikling/gpdb,tpostgres-projects/tPostgres,atris/gpdb,randomtask1155/gpdb,yazun/postgres-xl,0x0FFF/gpdb,tpostgres-projects/tPostgres,rubikloud/gpdb,adam8157/gpdb,zaksoup/gpdb,randomtask1155/gpdb,royc1/gpdb,lpetrov-pivotal/gpdb,lintzc/gpdb,yuanzhao/gpdb,ahachete/gpdb,kaknikhil/gpdb,rvs/gpdb,greenplum-db/gpdb,lintzc/gpdb,lintzc/gpdb,arcivanov/postgres-xl,zeroae/postgres-xl,cjcjameson/gpdb,xuegang/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,postmind-net/postgres-xl,zaksoup/gpdb,chrishajas/gpdb,lpetrov-pivotal/gpdb,yuanzhao/gpdb,tangp3/gpdb,zaksoup/gpdb,foyzur/gpdb,xuegang/gpdb,janebeckman/gpdb,atris/gpdb,rubikloud/gpdb,lpetrov-pivotal/gpdb,greenplum-db/gpdb,royc1/gpdb,yazun/postgres-xl,Chibin/gpdb,randomtask1155/gpdb,royc1/gpdb,adam8157/gpdb,Quikling/gpdb,jmcatamney/gpdb,zeroae/postgres-xl,ahachete/gpdb,foyzur/gpdb,zeroae/postgres-xl,royc1/gpdb,Chibin/gpdb,greenplum-db/gpdb,edespino/gpdb,xuegang/gpdb,greenplum-db/gpdb,tangp3/gpdb,Quikling/gpdb,yuanzhao/gpdb,pavanvd/postgres-xl,ashwinstar/gpdb,adam8157/gpdb,Chibin/gpdb,snaga/postgres-xl,techdragon/Postgres-XL,yuanzhao/gpdb,50wu/gpdb,adam8157/gpdb,lintzc/gpdb,ahachete/gpdb,kaknikhil/gpdb,techdragon/Postgres-XL,50wu/gpdb,arcivanov/postgres-xl,royc1/gpdb,CraigHarris/gpdb,zaksoup/gpdb,lisakowen/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,rubikloud/gpdb,cjcjameson/gpdb,adam8157/gpdb,jmcatamney/gpdb,0x0FFF/gpdb,Quikling/gpdb,zaksoup/gpdb,xinzweb/gpdb,arcivanov/postgres-xl,atris/gpdb,ovr/postgres-xl,yazun/postgres-xl,janebeckman/gpdb,Quikling/gpdb,0x0FFF/gpdb,xinzweb/gpdb,atris/gpdb,ahachete/gpdb,edespino/gpdb,Quikling/gpdb,tangp3/gpdb,foyzur/gpdb,foyzur/gpdb,foyzur/gpdb,arcivanov/postgres-xl,lintzc/gpdb,lisakowen/gpdb,ashwinstar/gpdb,snaga/postgres-xl,CraigHarris/gpdb,50wu/gpdb,janebeckman/gpdb,0x0FFF/gpdb,randomtask1155/gpdb,Chibin/gpdb,atris/gpdb,CraigHarris/gpdb,janebeckman/gpdb,royc1/gpdb,oberstet/postgres-xl,royc1/gpdb,Chibin/gpdb,xuegang/gpdb,atris/gpdb,yuanzhao/gpdb,jmcatamney/gpdb,xinzweb/gpdb,0x0FFF/gpdb,janebeckman/gpdb,Chibin/gpdb,ahachete/gpdb,janebeckman/gpdb,foyzur/gpdb,kaknikhil/gpdb,ovr/postgres-xl,chrishajas/gpdb,arcivanov/postgres-xl,rvs/gpdb,edespino/gpdb,50wu/gpdb,tangp3/gpdb,yuanzhao/gpdb,oberstet/postgres-xl,kmjungersen/PostgresXL,cjcjameson/gpdb,Chibin/gpdb,xinzweb/gpdb,rvs/gpdb,postmind-net/postgres-xl,ovr/postgres-xl,CraigHarris/gpdb,kaknikhil/gpdb,snaga/postgres-xl,ashwinstar/gpdb,techdragon/Postgres-XL,lpetrov-pivotal/gpdb,jmcatamney/gpdb,adam8157/gpdb,edespino/gpdb,lintzc/gpdb,rvs/gpdb,lpetrov-pivotal/gpdb,Quikling/gpdb,edespino/gpdb,kmjungersen/PostgresXL,zeroae/postgres-xl,ashwinstar/gpdb,techdragon/Postgres-XL,CraigHarris/gpdb,xuegang/gpdb,yuanzhao/gpdb