Update rand requirement from 0.5 to 0.6

Updates the requirements on [rand](https://github.com/rust-random/rand) to permit the latest version.
- [Release notes](https://github.com/rust-random/rand/releases)
- [Changelog](https://github.com/rust-random/rand/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-random/rand/commits/0.6.1)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot-support

Cargo.toml

@@ -22,7 +22,7 @@ serde-1    = ["ndarray/serde-1", "num-complex/serde"]
 [dependencies]
 lapacke = "0.2"
 num-traits  = "0.2"
-rand = "0.5"
+rand = "0.6"
 failure = "0.1"
 
 [dependencies.num-complex]