Pull request/d4fc7c24

[damiendr]

Added a method to get/set arrays by field name:

immutable Foo
    x::Float64
    a::Int32
end

soa = StructOfArrays(Foo, 10)

> soa[:a]
10-element Array{Int32,1}

> soa[:x] = linspace(0, 1, 10)
> soa[:x]
10-element Array{Float64,1}:
 0.0     
 0.111111
 0.222222
 0.333333
 0.444444
 0.555556
 0.666667
 0.777778
 0.888889
 1.0