Numerical comparison implemented

[GleammerRay]

1st commit implements the compare function itself.

2nd commit implements _get_num() for filling in numerical values (e.g. num_10 for 10.0 and num_10,01 for 10.01).

Merge it if you wish.

One thing to note, I am getting the following warning:

PerformanceWarning: DataFrame is highly fragmented.  This is usually the result of calling `frame.insert` many times, which has poor performance.  Consider joining all columns at once using pd.concat(axis=1) instead. To get a de-fragmented frame, use `newframe = frame.copy()`
  self[key] = self[left] < self[right]

I am not sure when it started appearing but I don't think it was there before the second commit so it needs further testing. Other than that everything seems to be working properly, I kept my changes minimal.

[GleammerRay]

Line 173 too long - split into two lines

[GleammerRay]

Apparently my formatting change broke syntax. Whoops! Had to fix that.

[jealous]

No worry, just take your time.

[codecov-commenter]

Codecov Report

Attention: 23 lines in your changes are missing coverage. Please review.

Comparison is base (9cb82d7) 98.20% compared to head (4ef0909) 96.04%.

Files	Patch %	Lines
stockstats.py	36.11%	23 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #184      +/-   ##
==========================================
- Coverage   98.20%   96.04%   -2.16%     
==========================================
  Files           1        1              
  Lines        1001     1037      +36     
==========================================
+ Hits          983      996      +13     
- Misses         18       41      +23     

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[jealous]

Thanks for the contribution. I think I will update the readme, contributor and tests in a later PR.