Add extensive testing and fixs issues

[smoia]

Closes #19

Proposed Changes

• Add extensive testing (Just above 90% mark cause workflow tree)
• Fix various little issues in package (breaking changes/fixes)
• Plenty of novelties to improve the code in general, especially refactoring side
• Fixed the masking of metrics

Change Type

• bugfix (+0.0.1)
• minor (+0.1.0)
• major (+1.0.0)
• refactoring (no version update)
• test (no version update)
• infrastructure (no version update)
• documentation (no version update)
• other

Checklist before review

• I added everything I wanted to add to this PR.
• [Code or tests only] I wrote/updated the necessary docstrings.
• [Code or tests only] I ran and passed tests locally.
• [Documentation only] I built the docs locally.
• My contribution is harmonious with the rest of the code: I'm not introducing repetitions.
• My code respects the adopted style, especially linting conventions.
• The title of this PR is explanatory on its own, enough to be understood as part of a changelog.
• I added or indicated the right labels.

• I added information regarding the timeline of completion for this PR.

• Please, comment on my PR while it's a draft and give me feedback on the development!

[codecov]

Codecov Report

Merging #16 (01340ff) into master (7573d7f) will increase coverage by 13.85%.
The diff coverage is 91.89%.

@@             Coverage Diff             @@
##           master      #16       +/-   ##
===========================================
+ Coverage   76.53%   90.38%   +13.85%     
===========================================
  Files          13       13               
  Lines        1061     1040       -21     
===========================================
+ Hits          812      940      +128     
+ Misses        249      100      -149     

Impacted Files	Coverage Δ
nigsp/io.py	91.12% <ø> (+1.77%)	⬆️
nigsp/operations/timeseries.py	92.47% <79.16%> (+10.19%)	⬆️
nigsp/workflow.py	73.23% <87.50%> (+0.12%)	⬆️
nigsp/blocks.py	94.54% <100.00%> (+55.25%)	⬆️
nigsp/cli/run.py	96.77% <100.00%> (ø)
nigsp/objects.py	100.00% <100.00%> (+18.86%)	⬆️
nigsp/operations/metrics.py	100.00% <100.00%> (+59.61%)	⬆️
nigsp/operations/surrogates.py	89.91% <100.00%> (+26.05%)	⬆️
nigsp/utils.py	95.12% <100.00%> (+0.38%)	⬆️
nigsp/viz.py	100.00% <100.00%> (+30.58%)	⬆️
... and 7 more