Add lockfile name options for send_queued_mail
Refactor send_queued_mail lockfile parameters
Merge pull request #56 from SeiryuZ/add-lockfile-option

Add lockfile name options for send_queued_mail
Use symbolic link based lock file.
Updated README.
Lockfile related cleanups.
Python 3 compatibility for lockfile.
Uncomment all tests.
Use a more Y-m-d date format in logutils.
Don't use more processes than number of emails.
Don't hardcode lockname in test.
Fixed lock_filename assignment.
Merge pull request #57 from ui/lock-file

Use symlink based locking to prevent race conditions
Updated documentation.
Bump version to 0.8.3.
Improved logging around file locking in send_queued_mail.
Added "--log-level" option to send_queued_mail
Updated README to document the new "log-level" argument.
Updated README
mail.send() now accepts "log_level" argument.