title: SemVer: can new functionality be considered breaking change?
body: <p>Consider a library that defines a class A, with several methods (A1, A2, ...), at version 1.0.0 (semantic versioning)</p>
  
  <p>Now imagine I add a new method to A object (method Ab). Is this a minor release? Because it adds functionality, and it shouldn't be a breaking change. 
  But if someone who's using the library declared a class A that extends class B, and B defines a method Ab with the same signature than the new method, now the code won't compile because it required the override declaration (in Scala and Java).</p>
  
  <p>So, is this a breaking change?</p>