Bump rand_core from 0.6.1 to 0.6.4

Bumps [rand_core](https://github.com/rust-random/rand) from 0.6.1 to 0.6.4.
- [Changelog](https://github.com/rust-random/rand/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-random/rand/compare/rand_core-0.6.1...0.6.4)

---
updated-dependencies:
- dependency-name: rand_core
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.lock

@@ -220,9 +220,9 @@ dependencies = [
 
 [[package]]
 name = "rand_core"
-version = "0.6.1"
+version = "0.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c026d7df8b298d90ccbbc5190bd04d85e159eaf5576caeacf8741da93ccbd2e5"
+checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
 dependencies = [
  "getrandom 0.2.2",
 ]
@@ -299,7 +299,7 @@ dependencies = [
 
 [[package]]
 name = "snake"
-version = "0.2.2"
+version = "0.2.3"
 dependencies = [
  "derive-error",
  "dirs",