Fix translation of 'COX-2 inhibition' in 'Laser Umbrella' article
Remove execution flag from 'neighbors.py' attributes
Update sitemap Pelican plugin to the current master revision

Fixes https://github.com/getpelican/pelican-plugins/issues/264
Updated from https://github.com/getpelican/pelican-plugins
Update extract_toc Pelican plugin to the current master revision

There isn't reason for this update, just for keep all plugins being actual.
Updated from https://github.com/getpelican/pelican-plugins
Lots of fixes for 'Balloon Car' article