Make if-not good example consistent with bad
Merge pull request #88 from ccfontes/patch-1

Make if-not good example consistent with bad
Existential: make mutation look like the exception
Merge pull request #90 from ccfontes/patch-2

Existential: make mutation look like the exception
Prefer vec over into when converting sequences to vectors
small fix: "forced to used" -> "forced to use"
Merge pull request #92 from felipebueno/patch-1

small fix: "forced to used" -> "forced to use"