log: accept removeCircular as an option to write

[ofrobots]

Callers of write (and related functions) can now pass removeCircular in
the options. This allows log entries to have circular references that
are replaced with '[Circular]' placeholder strings when encoded.

[googlebot]

So there's good news and bad news.

👍 The good news is that everyone that needs to sign a CLA (the pull request submitter and all commit authors) have done so. Everything is all good there.

😕 The bad news is that it appears that one or more commits were authored by someone other than the pull request submitter. We need to confirm that they're okay with their commits being contributed to this project. Please have them confirm that here in the pull request.

Note to project maintainer: This is a terminal state, meaning the cla/google commit status will not change from this state. It's up to you to confirm consent of the commit author(s) and merge this pull request when appropriate.

[coveralls]

Changes Unknown when pulling bd0038f on ofrobots:logging-removeCircular into ** on GoogleCloudPlatform:master**.

[ofrobots]

Do not land yet.

Turns out that this may not be the best way to do this – the options param to Log.prototype.write is expected to passed to the service (ie. is a service object). It is not acceptable for me to add a new property to it.

My preference would be to add a options object to the Log constructor. Thoughts?

[ofrobots]

Oh well, the browser hadn't refreshed. This is already landed. This isn't a big deal as-landed since no one is passing in removeCircular as an argument yet. Let me put together a follow-on.