Upgrade num-bigint to 0.4.0

Author: Armavica

Cargo.toml

@@ -31,7 +31,7 @@ quickcheck = { version = "0.9.2", default-features = false }
 ndarray-rand = "0.12"
 approx = "0.4"
 quickcheck_macros = "0.9"
-num-bigint = "0.3.1"
+num-bigint = "0.4.0"
 
 [[bench]]
 name = "sort"