BUG: missing status graphics for dag_ids with periods

[jlowin]

Based on some experimentation, it looks like status circles on the main web server page don't appear for dag_ids that contain periods. Changing a dag_id from test.dag to test_dag was enough to make the circles reappear. Since I can see the dag_stats json is generated correctly, perhaps this is a problem with how d3 interprets the json?

These are the circles I mean (note the missing middle row):

[jlowin]

Can confirm -- it's because the svg id can't contain periods. One hack that seems to work is to replace ".' with "__dot__" in the dag_id string.