Bump docopt 0.8 -> 1.1.0

Docopt is only used directly in the `render_readme` binary, though this
does transitively update some crates that are used in production.

Refs rust-lang#1265, rust-lang#1805

Author: jtgeibel

Cargo.lock

@@ -54,7 +54,7 @@ serde = { version = "1.0.0", features = ["derive"] }
 chrono = { version = "0.4.0", features = ["serde"] }
 comrak = { version = "0.4.0", default-features = false }
 ammonia = "2.0.0"
-docopt = "0.8.1"
+docopt = "1.0"
 scheduled-thread-pool = "0.2.0"
 derive_deref = "1.0.0"
 reqwest = "0.9.1"