Chore/remove test warnings

[danielorihuela]

Description

Closes #14.

Warnings have been removed and tarpaulin tests seem to work. Executing RUSTFLAGS="-C target-feature=+aes,+ssse3" cargo tarpaulin results in

Checklist

• [x] I have followed the Contribution Guidelines and Code of Conduct
• [x] I have commented my code following the OpenMined Styleguide
• [x] I have labeled this PR with the relevant Type labels No, because I cannot
• [x] My changes are covered by tests

[tholop]

Wonderful, thanks @danielorihuela -- and welcome!