bump version to 3.4.21 for development
bump version to 3.4.21 for development

chiemi627/postgresql,h4ck3rm1k3/postgresql,h4ck3rm1k3/postgresql,Unholster/postgresql,hw-cookbooks/postgresql,rastasheep/postgresql,eheydrick/postgresql,yakara-ltd/postgresql,rastasheep/postgresql,sous-chefs/postgresql,ozzyogkush/postgresql,yakara-ltd/postgresql,livepy/postgresql,hw-cookbooks/postgresql,GitBytes/postgresql,Unholster/postgresql,eheydrick/postgresql,chiemi627/postgresql,patcon/postgresql,sous-chefs/postgresql,ozzyogkush/postgresql,GitBytes/postgresql,livepy/postgresql,patcon/postgresql