🐞 Modify so E-Factor calculates when quality < 3

[alankan886]

• 🐞 Modify so E-Factor calculates when quality < 3.
• 📚 Modify docs according to the change and add note on misleading package title.

[codecov]

Codecov Report

Merging #9 (89a7e6e) into master (e350225) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master        #9   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            5         5           
  Lines          145       144    -1     
=========================================
- Hits           145       144    -1     

Impacted Files	Coverage Δ
supermemo2/model.py	100.00% <100.00%> (ø)

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