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
@@ -21,7 +21,7 @@
 license = "MIT/Apache-2.0"
 repository = "https://github.com/bluss/petgraph"
 [package.metadata.docs.rs]
-features = ["serde-1", "quickcheck"]
+features = ["serde-1"]
 
 [package.metadata.release]
 no-dev-version = true
@@ -40,11 +40,6 @@
 version = "0.3.0"
 optional = true
 
-[dependencies.quickcheck]
-version = "0.4"
-optional = true
-default-features = false
-
 [dependencies.serde]
 version = "1.0"
 optional = true
@@ -66,7 +61,7 @@
 version = "0.3"
 
 [features]
-all = ["unstable", "quickcheck", "stable_graph", "graphmap"]
+all = ["unstable", "stable_graph", "graphmap"]
 default = ["graphmap", "stable_graph"]
 generate = []
 graphmap = ["ordermap"]