added conversions file for large scale testing of file reading,writing issue #15
writing
Merge branch 'master' of github.com:ropensci/RNeXML
support arbitrary metadata elements in nexml_write
added constructor for meta and citation-type metdata #18
extend_phylo.R provides the nexmlTree class, #19
Added detection of datatype based on content value #18

Added the missing validator checks as part of the test_meta unit tests
that originally led me to overlook missing datatype declarations.
Added prism to the default namespaces, since we use it in the
citation metadata tool.  Updated documentation, including map
between R and xsd datatypes for basic classes.

All tests passing.
Add support for arbitrary rdfa/xml children of meta nodes

Closes #23
See the last test case in test_meta.R for an example.
add about string
update readme with metadata example
added a handful of metadata access methods
Includes methods: get_citation, get_license, get_metadata (top-level meta elements only)
summary (just uses phylo method for now, should display basic metadata too...).
methods are defined for nexml class, and extended to nexmlTree class
include ReferenceMeta
added support for adding identifiers using taxize, #24
still needs a real rel property instead of my fake ncbi:id, and needs support for other identifiers
handle namespaces explicitly, allowing for alternate definitions of their abbreviations
fix taxize to warn when no ID can be found
toTaxon added as rel for ResourceMeta in taxize
free memory after parsing XML
add treebase test script
Now handles case of some missing edge lengths, closes #29
add unit test showing rooted tree stays rooted #28