Update toml requirement from 0.5 to 0.7

Updates the requirements on [toml](https://github.com/toml-rs/toml) to permit the latest version.
- [Release notes](https://github.com/toml-rs/toml/releases)
- [Commits](toml-rs/toml@toml_datetime-v0.5.0...toml-v0.7.2)

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

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

Cargo.toml

@@ -35,7 +35,7 @@ rand_distr = "0.4"
 meval = "0.2"
 num = {version = "0.4", default-features = false}
 rust-embed = "6"
-toml = "0.5"
+toml = "0.7"
 clap = "2"
 config = "0.11"
 regex = "1.5"