Implement Krawczyk method

[Kolaru]

• Implement new contractor type Krawczyk and Krawczyk operator 𝒦
• Implement related tests
• Clean up and uniformized tests

[codecov-io]

Codecov Report

Merging #57 into master will increase coverage by 1.82%. The diff coverage is 95%.

@@            Coverage Diff             @@
##           master      #57      +/-   ##
==========================================
+ Coverage   46.31%   48.13%   +1.82%     
==========================================
  Files           9        9              
  Lines         339      349      +10     
==========================================
+ Hits          157      168      +11     
+ Misses        182      181       -1

Impacted Files	Coverage Δ
src/contractors.jl	95% <100%> (+1.66%)	:arrow_up:
src/roots.jl	85.24% <66.66%> (ø)	:arrow_up:
src/root_object.jl	25% <0%> (+12.5%)	:arrow_up:

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[dpsanders]

Looks good, thanks a lot!

[dpsanders]

Please don't include merge commits. I think you should be rebasing instead:

git checkout master
git pull upstream master

git checkout <your-branch>
git rebase master

Here, upstream is the remote that points to this repo.

[dpsanders]

Ah and then git push -f to force push the changes to the current branch.

[dpsanders]

Looks good to me, thanks a lot!