[#17] give the various tabs anchor tags
[#17] give the various tabs anchor tags

Allows people to link directly to specific tabs.

mxm/spark-pr-dashboard,d3borah/spark-pr-dashboard,d3borah/spark-pr-dashboard,databricks/spark-pr-dashboard,mengxr/spark-pr-dashboard,JoshRosen/spark-pr-dashboard,mxm/spark-pr-dashboard,mengxr/spark-pr-dashboard,JoshRosen/spark-pr-dashboard,databricks/spark-pr-dashboard,mengxr/spark-pr-dashboard,databricks/spark-pr-dashboard,mxm/spark-pr-dashboard,d3borah/spark-pr-dashboard