Save and load scalers

[FernandoVN98]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes #(issue_number)

Type of change

Please delete options that are not relevant.

• [ ] New algorithm or support class.
• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. If you haven't added any test and it is relevant provide instructions so we can reproduce.

• [ ] I have added a new test file: [E.g. test_rf.py]
• [x] I have added a new test case: [E.g. RFTest.test_make_classification]
• [x] I have tested it manually in a local environment.
• [ ] I have tested it manually in a supercomputer.

Reproduce instructions:

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas.
• [x] I have documented the public methods of any public class according to the guide styles.
• [x] I have made corresponding changes to the documentation
• [x] New and existing unit tests pass locally with my changes
• [x] I have rebased my branch before trying to merge.

[codecov[bot]]

Codecov Report

Merging #433 (98939ac) into master (bd3d9a6) will increase coverage by 83.06%. The diff coverage is 90.35%.

@@             Coverage Diff             @@
##           master     #433       +/-   ##
===========================================
+ Coverage   11.83%   94.89%   +83.06%     
===========================================
  Files          46       46               
  Lines        6532     6490       -42     
===========================================
+ Hits          773     6159     +5386     
+ Misses       5759      331     -5428     

Impacted Files	Coverage Δ
dislib/classification/knn/base.py	100.00% <ø> (+100.00%)	:arrow_up:
dislib/preprocessing/standard_scaler.py	94.00% <87.71%> (+0.66%)	:arrow_up:
dislib/preprocessing/minmax_scaler.py	95.68% <92.98%> (ø)

... and 38 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update bd3d9a6...98939ac. Read the comment docs.