initial work on git2 stuff

[CraZySacX]

• Migrate from git commands to git2.
• Add git, build, and rustc features to allow end users to disable output they may not want.
• Refactor
• CI/CD rework to use GitHub Actions and Codecov

[codecov]

Codecov Report

Merging #34 (04aa8ab) into master (8d522db) will increase coverage by 5.38%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           master       #34      +/-   ##
===========================================
+ Coverage   94.61%   100.00%   +5.38%     
===========================================
  Files           3        11       +8     
  Lines         130       492     +362     
===========================================
+ Hits          123       492     +369     
+ Misses          7         0       -7     

Impacted Files	Coverage Δ
src/config.rs	100.00% <100.00%> (ø)
src/constants.rs	100.00% <100.00%> (ø)
src/error/codes.rs	100.00% <100.00%> (ø)
src/error/mod.rs	100.00% <100.00%> (ø)
src/error/sources.rs	100.00% <100.00%> (ø)
src/feature/build.rs	100.00% <100.00%> (ø)
src/feature/git.rs	100.00% <100.00%> (ø)
src/feature/mod.rs	100.00% <100.00%> (ø)
src/feature/rustc.rs	100.00% <100.00%> (ø)
src/gen.rs	100.00% <100.00%> (ø)
... and 11 more

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