Add tls option to worker builder

[rustworthy]

This change is 

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 25.00000% with 21 lines in your changes missing coverage. Please review.

Project coverage is 67.3%. Comparing base (011b847) to head (af21d7d). Report is 1 commits behind head on chore/tech-debt.

Files	Patch %	Lines
src/worker/builder.rs	36.8%	12 Missing :warning:
src/tls/rustls.rs	0.0%	9 Missing :warning:

Additional details and impacted files

| [Files](https://app.codecov.io/gh/jonhoo/faktory-rs/pull/74?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jon+Gjengset) | Coverage Δ | | |---|---|---| | [src/tls/rustls.rs](https://app.codecov.io/gh/jonhoo/faktory-rs/pull/74?src=pr&el=tree&filepath=src%2Ftls%2Frustls.rs&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jon+Gjengset#diff-c3JjL3Rscy9ydXN0bHMucnM=) | `0.0% <0.0%> (ø)` | | | [src/worker/builder.rs](https://app.codecov.io/gh/jonhoo/faktory-rs/pull/74?src=pr&el=tree&filepath=src%2Fworker%2Fbuilder.rs&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jon+Gjengset#diff-c3JjL3dvcmtlci9idWlsZGVyLnJz) | `90.0% <36.8%> (-10.0%)` | :arrow_down: |

[rustworthy]

peer reviews, self reviews, upward reviews, quarterly reviews, and yearly reviews ... and code reviews

btw that was a sick reprise with an item and a half