fix: proper xmlify; nest transformation (UNTESTED)

* updated 'cheap_xmlify' to use SimpleXMLElement parsing instead
* nest transformation scans body array to break up slashed field keys
version, readme
fixed nesting, separator check, reattaching
added @attributes in doc
Merge pull request #2 from zaus/iss1-nested-fields

Merge features from branch Iss1 nested fields