Rationale: gitit is pretty fast without any caching, and this is simplest for most needs. Users who need caching can enable it explicitly, and they will then know about possible side-effects (e.g. the need to manually expire the cache after updating via the VCS). Updated caching documentation.
Thanks to Henry Laxen.
The file is self-documented using comments. Removed old data/SampleConfig.hs. Modified README to reflect new configuration method.