Heroku fingerprint gives false positives

[BBerastegui]

As seen here: EdOverflow/can-i-take-over-xyz#38

The Heroku detection needs extra checks apart from the one provided in the fingerprints file.

Now it's giving false positives in cases where the domain is .herokuapp.com.

[Rhynorater]

I also experienced this with herokudns.com. Sometimes it would find it and sometimes it would not. It could also not find domains that were domain -> Cloudfront/Cloudflare -> heroku. Even with the -a parameter.