Updates to README

[grayjeremy]

I got some errors when adding this to the notebook cell...maybe an update in the object definition? Also, may want to add a link to databricks docs on notebook cells, https://docs.databricks.com/notebooks/package-cells.html. I was going to PR this but stopped short because I'm not sure how these mismatches came about.

line 128
from: properties.put("jobResult", jobEnd.jobResult.toStringStart.jobId.toString)
to: properties.put("jobResult", jobEnd.jobResult.toString)

line 146:
from: metrics.put("attemptNumber", stageCompleted.stageInfo.attemptNumber)
to: metrics.put("attemptId", stageCompleted.stageInfo.attemptId)