Altered include statement as per feedback
Fixed boolean zen pointed out in feedback =]
Modified rooting function according to comments in feedback
Changed Array{T, 1} syntax to Vector{T}
Added variadic form of graft!() method.

Nothing special, just loops through all children provided and applies
the 1 parent 1 child graft!
Added tests to see if tree or node is empty.
Added checks that a node / tree is not completely empty to iterator constructors
Edited phylo.jl