removed problem where the nested items background color was showing up to the left of table headings (the "name" column)
fixed problem where top level category tables were having the title and id columns resizing when their content was expanded.

this was fixed by setting classes on the two columns and then setting the title column to be 20em wide; the second column (id) is set to have a width of auto.
fixed some more css styling issues (in support of #17)