Gcd floating point numbers fix

[fBruzja]

Do the checklist before submitting the PR:

• [✓] Have you read the guidelines mentioned in CONTRIBUTING.md?
• [✓] Have you squashed your commits?

Q: What version of Node.js you've used in the project? (e.g. Node v10.11.0)
A: v10.15.0

Q: Mention the Issue Number! (e.g. Fixed #8)
A: Fixed #192

• Give additional information regarding the PR below:

1. gcd function now supports floating point numbers
2. added another function that makes it possible for the result to round up to the maximum number of decimals the inputs had.
3. Added the relevant test case
4. Modified the documentation for the gcd function appropriately

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[codecov-io]

Codecov Report

Merging #218 into master will decrease coverage by 80.04%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master     #218       +/-   ##
===========================================
- Coverage     100%   19.95%   -80.05%     
===========================================
  Files          80       40       -40     
  Lines        1451      842      -609     
===========================================
- Hits         1451      168     -1283     
- Misses          0      674      +674

Impacted Files	Coverage Δ
src/binary-search-tree/index.js	5.47% <0%> (-94.53%)	⬇️
src/validation/argument-length.js	5.55% <0%> (-94.45%)	⬇️
src/frugal/index.js	7.69% <0%> (-92.31%)	⬇️
src/divide/index.js	9% <0%> (-91%)	⬇️
src/validation/count.js	9.09% <0%> (-90.91%)	⬇️
src/validation/number-array.js	11.11% <0%> (-88.89%)	⬇️
src/validation/frequency.js	11.11% <0%> (-88.89%)	⬇️
src/Matrix/index.js	11.49% <0%> (-88.51%)	⬇️
src/prime/index.js	12% <0%> (-88%)	⬇️
src/bell/index.js	13.33% <0%> (-86.67%)	⬇️
... and 69 more

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