should `deleteat!` be implemented for `OrderedDict` ?

[filchristou]

Currently deleteat! doesn't seem to work although i would personally expect it to.

julia> od = OrderedDict(UUID(1) => "ena", UUID(2) => "dio", UUID(3) => "tria", UUID(4) => "tessera")
OrderedDict{UUID, String} with 4 entries:
  UUID("00000000-0000-0000-0000-000000000001") => "ena"
  UUID("00000000-0000-0000-0000-000000000002") => "dio"
  UUID("00000000-0000-0000-0000-000000000003") => "tria"
  UUID("00000000-0000-0000-0000-000000000004") => "tessera"

julia> deleteat!(od, 3)
ERROR: MethodError: no method matching deleteat!(::OrderedDict{UUID, String}, ::Int64)
The function `deleteat!` exists, but no method is defined for this combination of argument types.

Closest candidates are:
  deleteat!(::BitVector, ::Integer)
   @ Base bitarray.jl:953
  deleteat!(::BitVector, ::Any)
   @ Base bitarray.jl:986
  deleteat!(::Vector, ::Integer)
   @ Base array.jl:1770
  ...

Stacktrace:
 [1] top-level scope
   @ REPL[33]:1

The implementation could be as easy as:

julia> mydeleteat!(od::OrderedDict, i::Int) = delete!(od, IterTools.nth(od, i)[1])
mydeleteat! (generic function with 1 method)

julia> mydeleteat!(od , 3)
OrderedDict{UUID, String} with 3 entries:
  UUID("00000000-0000-0000-0000-000000000001") => "ena"
  UUID("00000000-0000-0000-0000-000000000002") => "dio"
  UUID("00000000-0000-0000-0000-000000000004") => "tessera"

If you agree with adding this functionality let me know and I could do a PR.
In this case, if you find something wrong with mydeleteat implementation let me know.