Update NEWS for the v1.5.0 release.
Update NEWS for the v1.5.0 release.

Connexity/asynchbase,yuzhu712/asynchbase,nvoron23/asynchbase,nvoron23/asynchbase,adityakishore/asynchbase,mapr/asynchbase,OpenTSDB/asynchbase,tsuna/asynchbase,SteamShon/asynchbase,adityakishore/asynchbase,manolama/asynchbase,tempbottle/asynchbase,tempbottle/asynchbase,angushe/asynchbase,OpenTSDB/asyncbigtable,yuzhu712/asynchbase,Connexity/asynchbase,mway08/asynchbase,manolama/asyncbigtable,pythian/asynchbase,angushe/asynchbase,hhshuai/asynchbase,mapr/asynchbase,manolama/asynchbase,SteamShon/asynchbase,mway08/asynchbase,tsuna/asynchbase,hhshuai/asynchbase,OpenTSDB/asynchbase