Document the code

[Luni-4]

This PR fixes #139

To see the documentation, run the following command: cargo doc --open

[codecov-commenter]

Codecov Report

Merging #196 into master will increase coverage by 1.84%.
The diff coverage is 20.83%.

@@            Coverage Diff             @@
##           master     #196      +/-   ##
==========================================
+ Coverage   14.64%   16.49%   +1.84%     
==========================================
  Files          46       46              
  Lines        5839     5839              
  Branches      697      697              
==========================================
+ Hits          855      963     +108     
+ Misses       4707     4476     -231     
- Partials      277      400     +123     

Impacted Files	Coverage Δ
rust-code-analysis-cli/src/main.rs	0.00% <0.00%> (ø)
src/ast.rs	59.01% <ø> (ø)
src/asttools.rs	0.00% <ø> (ø)
src/comment_rm.rs	48.88% <ø> (ø)
src/count.rs	0.00% <ø> (ø)
src/find.rs	0.00% <0.00%> (ø)
src/function.rs	19.64% <ø> (ø)
src/langs.rs	90.00% <ø> (ø)
src/metrics/cyclomatic.rs	43.10% <ø> (ø)
src/metrics/exit.rs	44.68% <ø> (ø)
... and 20 more

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