Extend unix_socket support range

Author: sfackler

Cargo.toml

@@ -35,7 +35,7 @@ chrono = { version = "0.2.14", optional = true }
 openssl = { version = "0.6", optional = true }
 serde = { version = "0.3", optional = true }
 time = { version = "0.1.14", optional = true }
-unix_socket = { version = "0.3", optional = true }
+unix_socket = { version = ">= 0.3, < 0.5", optional = true }
 uuid = { version = "0.1", optional = true }
 
 [dev-dependencies]