Binomial, Factorial sequences added, existing updated with length parameter, minor refactors in AATreeTest, readme updated

[kolosovpetro]

Please include a summary of the change. Please also include relevant motivation and context (if applicable).

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[codecov]

Codecov Report

Merging #199 (0fb8cf0) into master (2c63986) will increase coverage by 0.01%.
The diff coverage is 94.59%.

@@            Coverage Diff             @@
##           master     #199      +/-   ##
==========================================
+ Coverage   92.52%   92.54%   +0.01%     
==========================================
  Files          95       97       +2     
  Lines        4348     4385      +37     
==========================================
+ Hits         4023     4058      +35     
- Misses        325      327       +2     

Impacted Files	Coverage Δ
Algorithms/Sequences/BinomialSequence.cs	92.85% <92.85%> (ø)
Algorithms/Sequences/FactorialSequence.cs	100.00% <100.00%> (ø)

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[siriak]

Thanks for your contribution! Could you make sequences infinite as they were before? Those sequences are infinite by their nature and we can take with .Take(n) or skip with .Skip(n) as many elements as we want.

[siriak]

Looks good, thank you!