Update exists-sync. Add relative path test.

[nathanhammond]

Closes #81. Stemming from the adoption of exists-sync.

Will track upstream fix at ember-cli/exists-sync#4.

[nathanhammond]

1. fs.existsSync has been un-deprecated making this an acceptable solution.
2. Upstream issue addressed as a bugfix for portions of the community who may still use that module.

---

• Land this PR. (@rwjblue)
• Release [email protected]. (@rwjblue)
• Grant npm privs to exists-sync to people. (@trabus)
• Release [email protected] via npm version patch. (@trabus)

[trabus]

I would be careful switching back, we added some additional checking for symlinks that link to symlinks. fs.existsSync will (or at least used to) give a false positive on a symlink that links to another symlink who's target has been removed.

If we can verify that fs.existsSync recursively follows symlinks until it hits something rather than giving a false positive, I’m fine switching. But if not, we’d hit some issues that we had previously run into.

[nathanhammond]

Now that upstream is fixed I'll rework this.

[stefanpenner]

+ [email protected]