Throw error on circular references

Currently the library does not throw error when parsing circual references.

Example:

const circular = {
   a : "value"
}
circular.a = circular
JSON.stringify(circular) //throws error

const circular = {
   a : "value"
}
circular.a = circular
qs.stringify(circular) //freezes computer 😣

[ljharb]

No, please leave them all open - whatever solution we go with, I’ll update all three PRs to have it as part of landing.

[ljharb]

Ok please stop creating extra PRs tho - each PR is a permanent ref on the repo, so how i have 3 PRs to keep in sync 😃