Drop some unused top-level dependencies

Author: Mark-Simulacrum

Cargo.lock

@@ -23,7 +23,6 @@ csv = "1.0.2"
 dotenv = "0.13"
 failure = "0.1.3"
 flate2 = "1"
-futures = "0.1.13"
 http = "0.1.10"
 hyper = "0.12.8"
 lazy_static = "1.0"
@@ -48,7 +47,6 @@ structopt-derive = "0.2"
 tar = "0.4.0"
 tempfile = "3.0.0"
 tera = "0.11.7"
-tokio = "0.1.11"
 toml = "0.4.6"
 url = "1.1"
 walkdir = "2"