Use pretty assertions!

hammond-downloader/Cargo.toml

@@ -18,3 +18,5 @@ failure_derive = "0.1.1"
 [dependencies.hammond-data]
 path = "../hammond-data"
 
+[dev-dependencies]
+pretty_assertions = "0.5.1"

hammond-downloader/src/lib.rs

@@ -9,6 +9,10 @@ extern crate failure_derive;
 #[macro_use]
 extern crate log;
 
+#[cfg(test)]
+#[macro_use]
+extern crate pretty_assertions;
+
 extern crate glob;
 extern crate hammond_data;
 extern crate hyper;