Add CHANGES.rst
Make SequenceTransform (a.k.a. transform) a class

This implies, that the initialization code needs to be executed only
once.
Make Document a more proper class

By integrating .dump, .transform, ._getstate methods.
Add support for predefined elements (a.k.a. templates)
Update CHANGES
Fix Decimal usage error
Merge pull request #5 from coldfix/predefined-elements

lengthes of predefined elements