Normalize whitespace via lstrip Jinja parameter

This adds the lstrip_blocks Jinja parameter and removes unnecessary
whitespace from a few notmyidea templates.

Note: The lstrip_blocks parameter requires Jinja 2.7+, which has been
noted in Pelican's setup.py.

Credit for this commit goes entirely to Russ Webber, who has earned my
eternal thanks for discovering and applying this useful Jinja parameter.

Refs #969