PostgresClientKit has a dependency on BlueSocket which, in turn, has a dependency on swift-argument-parser. Currently, BlueSocket requires swift-argument-parser v0.4.1..<1.0.0. This is a problem, because swift-argument-parser is currently at v1.1.3.

(Split from #41, which explores the bigger question of PostgresClientKit moving from BlueSocket/BlueSSLService to swift-nio.)