fix datetime slug
Merge pull request #14 from comzeradd/slug

fix datetime slug (2 digit months and days)

Before: /YYYY/M/D/slug/
After: /YYYY/MM/DD/slug/
Preparing for v0.9.9
extras/mk_redirect_list.py
extras/mk_redirect_list.py
mk_redirect_list.py will only print changed URLs.

The script will now print only URLs that have changed using the
new URL template (2-digit months and days).
Bug fix: render_archive_month used 1-digit months.
Bug fix.