Imports diagram: hovering

[GoogleCodeExporter]

It is theoretically possible to extend the diagram interactivity:
- hovering over classes/functions may bring up a tooltip with their docstrings
- recognising individual items [double] clicking (class, function, glob var, 
import item) and jump to the exact line of code in the corresponding source 
file.

Original issue reported on code.google.com by [email protected] on 6 May 2011 at 7:38