Split up the plugin implementation into two classes: one for markup templates (?genshi-markup? or just ?genshi?) and one for text templates (?genshi-text?). Also added an example for plain-text templating to the TurboGears example app.

This example shows how to transform some HTML input, while adding
elements such as headers, and using <em>/<strong> instead of <i>/<b>.
The output is that a proper XTHML document.