Add .gitignore.
Refactoring synchronized.py
Apply for python2.6.
Add a feature to a_thread to join terminated threads background.
Put implemnts should be run even after the pool is killed.
Fix pool.py. It could have been blocked forever on special timeing.
Add comment and tiny refactoring.
The argument check should be strict.
Change variable name.
Refactoring future.py.
Fix typo.
Fix typo.