Wrong handling of type parameter in tohrep of VPolygon

[mforets]

julia> p = rand(HPolygon);

julia> linear_map(rand(2, 2), p)
ERROR: TypeError: in Type{...} expression, expected UnionAll, got Type{HPolygon{Float64}}
Stacktrace:

 [1] tohrep(::VPolygon{Float64}, ::Type{HPolygon{Float64}}) at /Users/forets/.julia/dev/LazySets/src/VPolygon.jl:156
 [2] convert(::Type{HPolygon{Float64}}, ::VPolygon{Float64}) at /Users/forets/.julia/dev/LazySets/src/convert.jl:50
 [3] #linear_map#17(::Type{HPolygon{Float64}}, ::Function, ::Array{Float64,2}, ::HPolygon{Float64}) at /Users/forets/.julia/dev/LazySets/src/AbstractPolygon.
jl:209
 [4] linear_map(::Array{Float64,2}, ::HPolygon{Float64}) at /Users/forets/.julia/dev/LazySets/src/AbstractPolygon.jl:207
 [5] top-level scope at none:0