Crate authors like to put dev-dependencies in dependencies due to
https://github.com/rust-lang/cargo/issues/1596

Then due to lack of maintenance this pollutes the dependency set with old
crates that no longer compile.

Here, quickcheck 0.4 eventually depends on simd which no longer compiles.

--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,9 +22,6 @@
 [[test]]
 name = "tests"
 path = "tests.rs"
-[dependencies.quickcheck]
-version = "0.4.1"
-optional = true
 
 [features]
 default = ["std"]