polished up tests of geiger data, include validation
prefix nex: on type attribute value when writing to XML (for LiteralMeta and ResourceMeta)
basic simmap functions in place (#48)
could still be adjusted in several ways: tweaks to the XML definition
to define ordering and direction of ordering.  Could be extended to
include the node states defined in phytools.  The R mechanism needs
to fill out the remaining (sometimes non-essential or redundant)
parts of the phytools simmap slots.  The R mechanism still needs
to write the char/states part of the nexml and substitute state
names for state ids in the metadata