Minor fixes of typos, README and tests

[JanJereczek]

This PR:

• fixes the typos we had in the title of paper.md.
• provides an updated version of the README (with the correct installation information) and a description that is more coherent with the paper.
• the tests written for the slope_change.jl pipeline have been included in runtests.jl (a reason why our code coverage was lower than expected).
• (minor) additional tests for the change metrics.

[Datseris]

tests fail currently

[JanJereczek]

I noticed some errors in slope_change.jl and the associated significance, which were breaking the code. Also test/slope_change.jl had a couple bugs. They should be fixed now!

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.39%. Comparing base (80db37a) to head (84f1a3c).

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #77       +/-   ##
===========================================
+ Coverage   75.76%   86.39%   +10.63%     
===========================================
  Files          16       16               
  Lines         392      397        +5     
===========================================
+ Hits          297      343       +46     
+ Misses         95       54       -41     

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[Datseris]

Great, please increment patch version in Project.toml and tag a new release after merge!