Try handle unsolicited & clippy

[mordak]

While working on handling unsolicited responses in the other branch, bumped into these:

• Rename handle_unilateral to try_handle_unilateral because suggested here.
• Make clippy happy.

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This change is 

[codecov]

Codecov Report

Merging #184 (d0e61c7) into master (bd0a045) will increase coverage by 0.09%.
The diff coverage is 56.25%.

@@            Coverage Diff             @@
##           master     #184      +/-   ##
==========================================
+ Coverage   77.15%   77.24%   +0.09%     
==========================================
  Files          13       13              
  Lines        1593     1591       -2     
==========================================
  Hits         1229     1229              
+ Misses        364      362       -2     

Impacted Files	Coverage Δ
src/extensions/metadata.rs	60.00% <37.50%> (+1.46%)	⬆️
src/parse.rs	87.03% <66.66%> (ø)
src/client.rs	84.75% <100.00%> (ø)

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[jonhoo]

Great change, thanks!