port Phylogenetics.jl tests to FactCheck

I've ported the original Phylogenetics.jl tests to FactCheck and set up the module so the phylo contents can be used.

Some thoughts:

- this is probably not the best way to structure things. Do we want phylo to be a submodule?
- I've exported some methods that weren't exported in the original package - let's discuss the merits of the various exports.
- we should come up with more thorough test coverage