Add details link to status

[ashawley]

Right now, if the merge succeeds it says, "Continuous integration succeeded", or if it fails, "Failed to merge user-one:fix-2589: Conflicting". It would be nice to show the full log of the merge attempt.

This is an involved task, because (1) the log output needs to be extracted out (2) it needs to be web published somewhere, then (3) it's published location needs to added to the status API call.