Mark executable script as executable
Fix topological sort with many levels

The recursive topological sort algorithm hit Python's stack
limits when giving DAGs with large depths (e.g.
LinearDAG(10000)).  Use a stackless approach instead.  (Code
from the same author as the previous implementation.)
Add host and builder information in report

Fixes issue #10.
Fix missing newline in HTML

This doesn't affect anything but how pretty the HTML source
looks.