* Allow style names to be mapped by prefix. For instance:
r[style-name^='Code '] => code
* Add default style mappings for Heading 5 and Heading 6.
* Allow escape sequences in style IDs, style names and CSS class names.
* Allow a separator to be specified when HTML elements are collapsed.
* Add includeEmbeddedStyleMap option to allow embedded style maps to be
disabled.
* Include embedded styles when explicit style map is passed.