Added Config file support

[Niraj-Kamdar]

• ConfigParser class created.
• Added support for TOML (for sysadmins) and YAML (for devops users).
• Add tests for ConfigParser
• Add end-to-end tests for mixed use-case of command line + config file.
  closes: Discussion: Configuration file format #832

[codecov-commenter]

Codecov Report

Merging #846 into master will decrease coverage by 0.69%.
The diff coverage is 67.59%.

@@            Coverage Diff             @@
##           master     #846      +/-   ##
==========================================
- Coverage   88.60%   87.90%   -0.70%     
==========================================
  Files         160      162       +2     
  Lines        2606     2679      +73     
  Branches      281      289       +8     
==========================================
+ Hits         2309     2355      +46     
- Misses        232      254      +22     
- Partials       65       70       +5     

Flag	Coverage Δ
#longtests	87.90% <67.59%> (-0.70%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
test/test_config.py	0.00% <0.00%> (ø)
cve_bin_tool/config.py	80.00% <80.00%> (ø)
test/test_cli.py	98.49% <80.00%> (-1.51%)	⬇️
cve_bin_tool/cli.py	86.82% <82.60%> (+2.33%)	⬆️
cve_bin_tool/error_handler.py	86.00% <100.00%> (+0.28%)	⬆️
cve_bin_tool/version_scanner.py	86.08% <100.00%> (ø)
cve_bin_tool/cve_scanner.py	80.50% <0.00%> (-0.85%)	⬇️

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