Bump rust version to resolve builds

[jsturtevant]

Fixes #219

Switches to using https://rust-lang.github.io/rustup/overrides.html#the-toolchain-file

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 24.97%. Comparing base (693f4c5) to head (486b4e8). Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #223      +/-   ##
==========================================
+ Coverage   24.33%   24.97%   +0.64%     
==========================================
  Files          16       16              
  Lines        2655     2651       -4     
==========================================
+ Hits          646      662      +16     
+ Misses       2009     1989      -20     

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