Update readme about user registration.
Update readme about user registration.

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