Missing contractor for X^n

[dpsanders]

julia> X = IntervalBox(bareinterval(-10..10), 2)
ERROR: MethodError: no method matching IntervalBox(::BareInterval{Float64}, ::Int64)

Closest candidates are:
  IntervalBox(::Interval, ::Int64)
   @ IntervalBoxes ~/Dropbox/packages/IntervalBoxes/src/intervalbox.jl:123
  IntervalBox(::IntervalBox, ::Any)
   @ IntervalBoxes ~/Dropbox/packages/IntervalBoxes/src/intervalbox.jl:31
  IntervalBox(::Union{BareInterval{T}, Interval{T}} where T)
   @ IntervalBoxes ~/Dropbox/packages/IntervalBoxes/src/intervalbox.jl:23
  ...