a few docs updates

Author: ExpandingMan

README.md

@@ -9,14 +9,14 @@ A package for dealing with generalized tree-like data structures.
 
 ## Examples
 ```julia
-julia> t = [[1,2], [3,4]];  # collections in Base are trees
+julia> t = [[1,2], [3,4]];  # AbstractArray and AbstractDict are trees
 
 julia> children(t)
 2-element Vector{Vector{Int64}}:
  [1, 2]
  [3, 4]
 
-julia> childindex(t, (2,1))
+julia> getdescendant(t, (2,1))
 3
 
 julia> collect(PreOrderDFS(t))  # iterate from root to leaves

docs/src/faq.md

@@ -79,9 +79,10 @@ several major obstacles
 All of this means that you are unlikely to get type-stable code from AbstractTrees.jl without some
 effort.
 
-The simplest way around this is to define the `eltype` of tree iterators via
+The simplest way around this is to define the `NodeType` trait and `nodetype` (analogous to
+`Base.IteratorEltype` and `eltype`):
 ```julia
-Base.NodeType(::Type{<:ExampleNode}) = HasNodeType()
+AbstractTrees.NodeType(::Type{<:ExampleNode}) = HasNodeType()
 AbstractTrees.nodetype(::Type{<:ExampleNode}) = ExampleNode
 ```
 which is equivalent to asserting that all nodes of a tree are of the same type.  Performance