Improve the rntxt output writer.

[napulen]

Fixes #68

• No need to "autocorrect" rntxt files. Output the number of measures the model wants to output.
• Fix the syntax of beats, changes of key, and Roman numerals

[codecov-commenter]

Codecov Report

Merging #81 (be76bbb) into main (0c91b48) will increase coverage by 0.49%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main      #81      +/-   ##
==========================================
+ Coverage   74.95%   75.45%   +0.49%     
==========================================
  Files          47       47              
  Lines        2380     2363      -17     
==========================================
- Hits         1784     1783       -1     
+ Misses        596      580      -16     

Impacted Files	Coverage Δ
AugmentedNet/inference.py	14.72% <0.00%> (+0.83%)	⬆️

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