Various fixes related to updated upstream toolchain

[Fluxie]

This should fix the unit test errors that surfaced in my other pull request.

[codecov-io]

Codecov Report

Merging #61 into master will increase coverage by 0.09%. The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master      #61      +/-   ##
==========================================
+ Coverage   76.63%   76.73%   +0.09%     
==========================================
  Files          48       49       +1     
  Lines        3116     3120       +4     
==========================================
+ Hits         2388     2394       +6     
+ Misses        728      726       -2

Impacted Files	Coverage Δ
intercom/src/lib.rs	37.5% <ø> (+7.5%)	:arrow_up:
intercom-common/tests/parse_tests.rs	96.77% <ø> (ø)	:arrow_up:
intercom-common/src/builtin_model.rs	95.65% <ø> (ø)	:arrow_up:
intercom/src/interfaces.rs	0% <0%> (ø)
intercom-common/src/utils.rs	91.27% <100%> (+0.58%)	:arrow_up:
intercom-attributes/tests/lib.rs	86.36% <100%> (ø)	:arrow_up:
intercom-common/src/model.rs	89.34% <100%> (+0.12%)	:arrow_up:
intercom/src/classfactory.rs	67.39% <0%> (-0.7%)	:arrow_down:
intercom/src/error.rs	13.15% <0%> (+0.11%)	:arrow_up:
... and 1 more

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[Rantanen]

Thanks!