Add support for python setup.py develop.

pytools/__init__.py

pytools/arithmetic_container.py

pytools/batchjob.py

pytools/datatable.py

pytools/decorator.py

pytools/diskdict.py

pytools/grid.py

pytools/lex.py

pytools/log.py

pytools/prefork.py

pytools/refdebug.py

pytools/runalyzer.py

pytools/stopwatch.py

setup.py