v0.2.0

- release version
- added segment length checking
- after much trial and error, settled for clojure.xml instead of
  clojure.data.xml as the XML representation; reasons:
    - much of the XML construction code for segmentation checking would need to
      be refactored (:content is represented a list instead of a vector, which
      means we can't index into it); I might do this in the future, but no
      earlier than Clojure 1.6, because...
    - clojure.walk fails on clojure.data.xml, because it doesn't work on records
      (it will starting with Clojure 1.6)