Fix test failure

As reported in

    hjson/hjson-rust#23

the issue of the failing tests is the serde_hjson crate. The problem can
be prevented (as reported by
hjson/hjson-rust#23 (comment)) by
disabling the default features of the crate (namingly preservation of
key order).

This commit disables the default features of serde_hjson to fix our
tests.

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>

Author: matthiasbeyer

Cargo.toml

@@ -28,7 +28,7 @@ nom = "5.0.0"
 toml = { version = "0.5", optional = true }
 serde_json = { version = "1.0.2", optional = true }
 yaml-rust = { version = "0.4", optional = true }
-serde-hjson = { version = "0.9", optional = true }
+serde-hjson = { version = "0.9", default-features = false, optional = true }
 rust-ini = { version = "0.13", optional = true }
 
 [dev-dependencies]