Hello,

I have a problem with discrete and continous variable, I want to use CPLEX with MultiJuMP, but I get this error :

```
ERROR: MethodError: no method matching NonlinearModel(::CPLEX.CplexSolver)
Closest candidates are:
NonlinearModel(::Ipopt.IpoptSolver) at /home/monpc/.julia/v0.6/Ipopt/src/IpoptSolverInterface.jl:28
NonlinearModel(::Int64) at /home/monpc/.julia/v0.6/MathProgBase/src/SolverInterface/SolverInterface.jl:27
NonlinearModel() at /home/monpc/.julia/v0.6/MathProgBase/src/SolverInterface/SolverInterface.jl:25
Stacktrace:
[1] _buildInternalModel_nlp(::JuMP.Model, ::JuMP.ProblemTraits) at /home/monpc/.julia/v0.6/JuMP/src/nlp.jl:1246
[2] #build#119(::Bool, ::Bool, ::JuMP.ProblemTraits, ::Function, ::JuMP.Model) at /home/monpc/.julia/v0.6/JuMP/src/solvers.jl:303
[3] (::JuMP.#kw##build)(::Array{Any,1}, ::JuMP.#build, ::JuMP.Model) at ./<missing>:0
[4] #solve#116(::Bool, ::Bool, ::Bool, ::Array{Any,1}, ::Function, ::JuMP.Model) at /home/monpc/.julia/v0.6/JuMP/src/solvers.jl:168
[5] (::JuMP.#kw##solve)(::Array{Any,1}, ::JuMP.#solve, ::JuMP.Model) at ./<missing>:0
[6] _solve_nbi(::JuMP.Model, ::Bool) at /home/monpc/.julia/v0.6/MultiJuMP/src/MultiJuMP.jl:180
[7] #solvehook#11(::Symbol, ::Bool, ::Array{Any,1}, ::Function, ::JuMP.Model) at /home/monpc/.julia/v0.6/MultiJuMP/src/MultiJuMP.jl:333
[8] (::MultiJuMP.#kw##solvehook)(::Array{Any,1}, ::MultiJuMP.#solvehook, ::JuMP.Model) at ./<missing>:0
[9] #solve#116(::Bool, ::Bool, ::Bool, ::Array{Any,1}, ::Function, ::JuMP.Model) at /home/monpc/.julia/v0.6/JuMP/src/solvers.jl:151
[10] (::JuMP.#kw##solve)(::Array{Any,1}, ::JuMP.#solve, ::JuMP.Model) at ./<missing>:0
```

How I can solve it ? thanks