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Closes #14
Rule for by-name right associative operators

Warnings for the issue presented in SI-1980:
https://issues.scala-lang.org/browse/SI-1980
Merge pull request #15 from Lewix/bynamerightassociative

Warn about by-name right associative operators
Rule for PackageObjectClasses

Warnings for the issue presented in SI-4344:
https://issues.scala-lang.org/browse/SI-4344
Merge pull request #16 from Lewix/packageobjectclasses

Rule for PackageObjectClasses
Warn about usage of `List` operations that have a linear cost