add a 'cols' argument so we print 99 columns max, similar to str
doc update
silence CRAN warning
melt_ now performs similarly to melt(..., id=NULL), if id not specified
clean up some of the 'misc' functions
prefer R swap implementation
unmelt -> unmelt_, to reflect the link
transpose_list transposes a matrix-like list, to a new list
refactor some C code
docs, minor changes