Mute warnings.

If the cached file does not yet exist, PHP (depending on error_level) will throw an annoying warning in the error log.
Add a favicon.

This is just the favicon from
http://showrss.karmorra.info/static/favicon.ico
Add a robots.txt

Presumably there's nothing to be crawled anyways.
Add .gitignore

Ignore the contents of the cache/ folder.
Merge branch 'add_robots'
Merge remote-tracking branch 'origin/add_gitignore'
Merge remote-tracking branch 'origin/mute_php_file_warnings'