unnecessary lines removed from app.yaml

- if expiration defined in all static handlers
  general expiration declaring is won't affect
.hgignore removed

1. Now it's git repo. Not a mercurial repo.
2. `*.pyc` already (default) written in gitignore global
pep8 compatible changes. except line length
bot friendly changes

- It's better for HEAD allowed in `/robots.txt`, `/sitemap.xml`.
  Most bots often send HEAD request before actual GEt request.
required is False as default
readability of hash.html improved a bit