fix(circular deps): Improve error messages

As we don't check for circular dependencies before a given depth
threshold is reached we had messages like:

    "A -> B -> A -> B -> A -> ... -> A"

This commit implements a deduplication to have only:

    "A -> B -> A"
Merge pull request #101 from vicb/0514-circ

fix(circular deps): Improve error messages
style(error helper): improve readability
Merge pull request #103 from vicb/style-readability

style(error helper): improve readability