Upgrade the linux builds to use focal

[palfrey]

Eoan has been EoL'ed and hence the lack of release files anymore. See https://fridge.ubuntu.com/2020/07/17/ubuntu-19-10-eoan-ermine-end-of-life-reached-on-july-17-2020/

I've also fixed a set of Clippy lints that were now firing with newer Rust and made the build break.

[codecov-io]

Codecov Report

Merging #47 (19a3a0f) into master (1323d5f) will decrease coverage by 0.00%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #47      +/-   ##
==========================================
- Coverage   65.38%   65.37%   -0.01%     
==========================================
  Files           4        4              
  Lines        3446     3437       -9     
==========================================
- Hits         2253     2247       -6     
+ Misses       1193     1190       -3     

Impacted Files	Coverage Δ
src/lib.rs	65.11% <100.00%> (-0.01%)	:arrow_down:
src/tests.rs	80.46% <0.00%> (+0.05%)	:arrow_up:

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[mheese]

@palfrey Thanks for the PR! And I apologize for only looking at this now. I will have some time next week to look into this, and I plan in general to make some progress then.

[palfrey]

@palfrey Thanks for the PR! And I apologize for only looking at this now. I will have some time next week to look into this, and I plan in general to make some progress then.

How's this going?

[mheese]

Closing all PRs together with the deprecation notice on the README. Please switch to the cryptoki crate which doesn't have this problem to begin with https://github.com/parallaxsecond/rust-cryptoki