Fix the invalid CSR generation

Due to a bug in the `acme-lib` dependency, the Certificate Signing
Request was not built correctly. This issue caused the ACME server to
reject such CSR when ordiring more than two domains.
algesten/acme-lib#3

acmed/Cargo.toml

@@ -11,7 +11,7 @@ license = "MIT OR Apache-2.0"
 include = ["src/**/*", "Cargo.toml", "LICENSE-*.txt"]
 
 [dependencies]
-acme-lib = "0.4"
+acme-lib = "0.5"
 clap = "2.32"
 daemonize = "0.3"
 env_logger = "0.6"