Really Simple Content Cache: Cache content in files

This class can be used to cache content in files.

It can check if a given cache file exists and it has not expired. In that case it returns the cached content stored in the cache file.

If the cache file does not exist or the cached content has expired, the cache file may be refreshed with new content.

The class may also invalidate cached content by removing the respective file if it exists.

The cache expiry time and the cache file name extension are configurable details.