[#120] Add a convenient way to bind data to phylo4d objects

Yes it's resolved. But it's only possible to pass a full data frame.

foo <- addData(foo, node.data=someNodeData)

I can't guarantee what happens if you try to do something like:
tdata(foo)[1,2] <- rnorm(1)

We don't have any methods (as far as I know) to deal with [<- in phylobase. These are fairly tricky to write in S4 from what I can remember...

This may be difficult: There is an existing <- method for tdata/phylo4d, but since tdata(foo) and foo[,'trait1'] return a data.frame, the <- method for phylo4d is never called when the commands above are invoked (the base <- method is used), no error checking occurs, and bad things happen. Suggest removing these methods until we sort this out.