Update zerocopy requirement from 0.5.0 to 0.6.0

Updates the requirements on zerocopy to permit the latest version.

---
updated-dependencies:
- dependency-name: zerocopy
  dependency-type: direct:production
...

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

Author: dependabot[bot]

Cargo.toml

@@ -68,7 +68,7 @@ rand_distr = "0.3"
 quickcheck = "0.9"
 log = "0.4.14"
 env_logger = "0.9.0"
-zerocopy = "0.5.0"
+zerocopy = "0.6.0"
 byteorder = "1.4.3"
 
 [[test]]