update README

Author: ChrisRackauckas

README.md

@@ -8,6 +8,23 @@
 RecursiveArrayTools.jl is a set of tools for dealing with recursive arrays like
 arrays of arrays. The current functionality includes:
 
+### Types
+
+```julia
+ArrayPartition(x::AbstractArray...)
+```
+
+An `ArrayPartition` `A` is an array which is made up of different arrays `A.x`.
+These index like a single array, but each subarray may have a different type.
+However, broadcast is overloaded to loop in an efficient manner, meaning that
+`A .+= 2.+B` is type-stable in its computations, even if `A.x[i]` and `A.x[j]`
+do not match types. A full array interface is included for completeness, which
+allows this array type to be used in place of a standard array in places where
+such a type stable broadcast may be needed. One example is in heterogeneous
+differential equations for [DifferentialEquations.jl](https://github.com/JuliaDiffEq/DifferentialEquations.jl). 
+
+### Functions
+
 ```julia
 recursivecopy!(b::Array{T,N},a::Array{T,N})
 ```
@@ -33,3 +50,16 @@ copyat_or_push!{T}(a::AbstractVector{T},i::Int,x)
 
 If `i<length(x)`, it's simply a `recursivecopy!` to the `i`th element. Otherwise it will
 `push!` a `deepcopy`.
+
+```julia
+recursive_one(a)
+```
+
+Calls `one` on the bottom container to get the "true element one type"
+
+```julia
+mean{T<:AbstractArray}(vecvec::Vector{T})
+mean{T<:AbstractArray}(matarr::Matrix{T},region=0)
+```
+
+Generalized mean functions for vectors of arrays and matrix of arrays.