Code review comment for lp:~allenap/launchpad/more-retest

This branch adjusts retest.py to allow pasting of a test report (by
using fileinput), changes the parsing code to work with multiple
chunks (so test output can be appended to a log), makes it *not* run
the whole test suite if it doesn't find any tests in the log, improves
the usage docs, and MOST IMPORTANTLY makes it possible to kill the
test process with Ctrl-C, which was especially important in the days
when it could decide to try and run the whole test suite.

It also moves the script to be a buildout template, which ends up
creating bin/retest (currently it's not a template, and lives in
utilities/retest.py).