Fix logs with local scheduler

[jacobtomlinson]

Should fix #231.

Switched the scheduler logs method to get_logs and added a shim to the Scheduler object to ensure compatibility.

Added tests for both remote and local schedulers.

[mrocklin]

+1 from me. Alternatively, should we rename get_logs to logs upstream? I'm ambivalent on the change, just thought I'd bring it up.

[jacobtomlinson]

I have a slight preference for logs but I do not have strong feelings.

[mrocklin]

Then I say go for it. Part of my motivation here is also to make sure that you feel comfortable changing things upstream, and not just in dask-kubernetes.

[quasiben]

With dask/distributed#3473 is this PR still needed ?

[jacobtomlinson]

Potentially logs should be renamed to get_logs and logs should be reinstated as the shim for backward compatibility.