Bump: support manual version

[jakob-keller]

Description

Closes #435

Checklist

• Add test cases to all the changes you introduce
• Run ./scripts/format and ./scripts/test locally to ensure this change passes linter check and test
• Test the changes on the local machine manually
• Update the documentation for the changes

Expected behavior

cz bump 1.2.3 uses 1.2.3 as new version

Steps to Test This Pull Request

Additional context

[codecov]

Codecov Report

Base: 98.38% // Head: 98.40% // Increases project coverage by +0.01% 🎉

Coverage data is based on head (2ba0b73) compared to base (f6ab845).
Patch coverage: 96.77% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #591      +/-   ##
==========================================
+ Coverage   98.38%   98.40%   +0.01%     
==========================================
  Files          39       39              
  Lines        1614     1634      +20     
==========================================
+ Hits         1588     1608      +20     
  Misses         26       26              

Flag	Coverage Δ
unittests	98.40% <96.77%> (+0.01%)	⬆️

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

Impacted Files	Coverage Δ
commitizen/cli.py	93.93% <ø> (ø)
commitizen/commands/bump.py	97.03% <96.29%> (+0.42%)	⬆️
commitizen/__version__.py	100.00% <100.00%> (ø)
commitizen/exceptions.py	100.00% <100.00%> (ø)

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[jakob-keller]

Not sure, why these tests fail. Anything I need to fix?

[woile]

Tests are not failing, it is the coverage report. But I'm not sure why it's decreasing, it doesn't look like it's decreasing

[Lee-W]

Tests are not failing, it is the coverage report. But I'm not sure why it's decreasing, it doesn't look like it's decreasing

Sometimes I just don't understand codecov 🤔

[woile]

Thanks for this nice feature!