Add support for publishing the author logo to s3

This will be used by the template analyzer service to
rewrite authorLogo from a template-author-provided URL
to a URL hosted on our S3.
Allow authorLogo to be longer, and no newlines in links

We used paragraph check for links, which let regular links
be too long and kept data links too short. So clean this up.
Also, no newlines in links, because weird.
Handle missing S3 metadata object

This is a theory about a null pointer exception; the commit
also adds better logging where the exception occurs.
Merge pull request #27 from typesafehub/wip/havocp-author-logo

Add support for publishing the author logo to s3