Remove obsolete docopt dependency

Author: Turbo87

Cargo.lock

@@ -51,7 +51,6 @@ ctrlc = { version = "3.0", features = ["termination"] }
 derive_deref = "1.1.1"
 diesel = { version = "1.4.0", features = ["postgres", "serde_json", "chrono", "r2d2"] }
 diesel_full_text_search = "1.0.0"
-docopt = "1.0"
 dotenv = "0.15"
 env_logger = "0.8"
 failure = "0.1.1"