The test for the Polynomials package are now failing in v0.5. Before
```
p1 = Poly([1, 2])
p = [p, p] # 2-element Array{Polynomials.Poly{Float64},1}:
p + 3 # 2-element Array{Polynomials.Poly{Float64},1}:
```
But now, `p+3` is an `Array{Any,1}`. I think the solution is related to how
`promote_array_type` uses `promote_op`, which in turn returns `Any` for
`Base.promote_op(:+, eltype(p), eltype(3))`. There is a comment in
promotion.jl about adding methods to `promote_op`, but as `promote_op`
isn't exported this seems like the wrong solution for this case. (As well,
I couldn't figure out exactly how to do so.) I could also fix this by
defining `.+` to directly call `broadcast`, but that defeats the work in
`arraymath,jl`.
Any hints?
