CoinbaseController: return 200 response on webhook exception.

Coinbase will silently disable sending webhook notifications if it
receives too many 403/error responses.
Don't allow friend api operations on FakeSubreddits.
Use ModeratorMessageBuilder when viewing a modmail permalink.

Previously had been using UserMessageBuilder which does not include
replies when viewed by moderators.
Fix: URL type for geoip_location.

Fixes this error message in the default configuration:
reddit-paster: Failed to fetch GeoIP information: URLError('unknown url
type: 127.0.0.1',)
Remove reddit-ie6-hax.css and reddit-ie7-hax.css from the Makefile.

The source files were removed.
Remove unneeded execute permissions.