Allow kubectl ate logs to filter by container and supervisor

[juli4n]

We should add kubectl ate logs a way to specify whether you want all logs (default), logs for a specific container, or the ateom supervisor logs.

After #290 everything is actually in place, this should be just changes to the kubectl-ate client.

Haven Xia (@HavenXia) Benjamin Elder (@BenTheElder)

[MayorFaj]

/assign

[BenTheElder]

I'm not sure if we want to call it "supervisor" but I'm also not sure if we want to call it "ateom" either ... this is a leaky implementation detail. cc Taahir Ahmed (@ahmedtd)