New in this version:
- Adds format identifier "xhtml"
- Adds identifier for text files
- Adds more options to Text2ObflTask
- Remove xml properties from "html" identifier implementation
- Removes "html" and "txt" format identifiers
- Removes xml:lang validation
- Removes a debug message in the epub converter
- Removes a transient dependency from jing
- Improve task names
- Improves javadoc