Add --version, option.client, and update README

[cgewecke]

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[codecov-io]

Codecov Report

Merging #393 into truffle-plugin will increase coverage by 0.03%.
The diff coverage is 100%.

@@                Coverage Diff                 @@
##           truffle-plugin     #393      +/-   ##
==================================================
+ Coverage           94.41%   94.44%   +0.03%     
==================================================
  Files                  10       10              
  Lines                 519      522       +3     
==================================================
+ Hits                  490      493       +3     
  Misses                 29       29

Impacted Files	Coverage Δ
lib/ui.js	100% <ø> (ø)	⬆️
lib/app.js	91.09% <100%> (ø)	⬆️
dist/truffle.plugin.js	96.72% <100%> (+0.16%)	⬆️

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