fix 0.4 warning
fix 0.4 warning

JuliaPackageMirrors/BlackBoxOptim.jl,JuliaPackageMirrors/BlackBoxOptim.jl,multidis/BlackBoxOptim.jl,tkelman/BlackBoxOptim.jl,JuliaPackageMirrors/BlackBoxOptim.jl,multidis/BlackBoxOptim.jl,multidis/BlackBoxOptim.jl,tkelman/BlackBoxOptim.jl,tkelman/BlackBoxOptim.jl