Added nCrCatalan to MathBall

[pydevsg]

Do the checklist before submitting the PR:

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

Q: What version of Node.js you've used in the project? (e.g. Node v10.11.0) A:v11.6.0

Q: Mention the Issue Number! (e.g. Fixed #8) A:Fixed Issue #127

• Give additional information regarding the PR below: Added nCrCatalan() which uses existing nCr module and shortens the method of finding Nth Catalan number.

[codecov-io]

Codecov Report

Merging #139 into master will decrease coverage by 75.82%. The diff coverage is 36.36%.

@@             Coverage Diff             @@
##           master     #139       +/-   ##
===========================================
- Coverage     100%   24.17%   -75.83%     
===========================================
  Files          78       79        +1     
  Lines        1263     1274       +11     
===========================================
- Hits         1263      308      -955     
- Misses          0      966      +966

Impacted Files	Coverage Δ
src/index.js	100% <100%> (ø)	:arrow_up:
src/nCrCatalan/index.js	30% <30%> (ø)
src/validation/argument-length.js	5.55% <0%> (-94.45%)	:arrow_down:
src/frugal/index.js	7.69% <0%> (-92.31%)	:arrow_down:
src/length/index.js	8.33% <0%> (-91.67%)	:arrow_down:
src/matrixMultiply/index.js	8.33% <0%> (-91.67%)	:arrow_down:
src/division/index.js	9% <0%> (-91%)	:arrow_down:
src/validation/count.js	9.09% <0%> (-90.91%)	:arrow_down:
src/stack/index.js	9.52% <0%> (-90.48%)	:arrow_down:
src/permutation/index.js	9.52% <0%> (-90.48%)	:arrow_down:
... and 70 more

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