Deprecating RobotsTxt::deny in favor of disallow.
Remove fences in README.
Refactor creation of loc elements.
Simplify: deprecate txt format.
Removing tests for deprecated format.
Extracting siteindex functionality from sitemap class.

Deprecating format usage in Sitemap::generate.
Splitting tests.
Adding base class.
Lowercasing all variables; as per Lithium Coding Standard.
Rewording docblocks.
Updating README with usage on siteindex.
Adding docblock for Siteindex class.