Default Options Change

Planning out configuration and API for the parse
tree. Changes from 1.x:

- "CSS_PRE" and "CSS_PRE_ID" have been merged into
  one single alias: "cssPrefix"
- Replaced "XHTML" with "target", case insensitive.
  If the targeted markup language name is supported,
  the tree will render.

  Currently still "XHTML" and "HTML".