chore(deps): bump structopt from 0.3.3 to 0.3.4

Bumps [structopt](https://github.com/TeXitoi/structopt) from 0.3.3 to 0.3.4.
- [Release notes](https://github.com/TeXitoi/structopt/releases)
- [Changelog](https://github.com/TeXitoi/structopt/blob/master/CHANGELOG.md)
- [Commits](https://github.com/TeXitoi/structopt/compare/v0.3.3...v0.3.4)

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

Cargo.toml

@@ -29,7 +29,7 @@ log = "0.4.8"
 pretty_env_logger = "0.3.1"
 serde = "1.0.102"
 serde_json = "1.0.41"
-structopt = "0.3.3"
+structopt = "0.3.4"
 tokio = "0.1.22"
 tokio-codec= "0.1.1"
 tokio-io= "0.1.12"