Send comments as robotComments (#238)

[marquiswang]

Robot comments show up in the Findings tab, instead of in the comments. This makes it much easier to differentiate from them a reviewer's comments.

The API requires a "runId" for the comment. I've chosen to just send a random UUID for now, but eventually we could wire in something like a build number or something.

[marquiswang]

@SpOOnman extremely belatedly, here's another version.