Cannot override isClean #16
Description
When I override isClean in a subclass of StackTracey, the original method is called instead.
This does not happen with isThirdParty, which I can override no problem: indeed, my override of isThirdParty is correctly called by the original isClean.
I believe this problem arises because mergeRepeatedLines calls new StackTracey, rather than constructing the current class. The same problem is present in withSourcesAsync(), and in the array methods, so that even overriding clean() is not sufficient to prevent an isClean being ignored.