URL updates : JuliaOpt -> jump-dev (#35)

Author: blegat

pages/code.md

@@ -5,9 +5,9 @@ title:  "The JuMP ecosystem"
 The JuMP project consists of the main [JuMP](https://github.com/juliaopt/JuMP.jl)
 package, and a large collection of supporting Julia packages.
 
-The JuMP source code can be found at [https://github.com/JuliaOpt/JuMP.jl](https://github.com/JuliaOpt/JuMP.jl).
+The JuMP source code can be found at [https://github.com/jump-dev/JuMP.jl](https://github.com/jump-dev/JuMP.jl).
 
-Beneath JuMP, there is an abstraction layer called MathOptInterface ([source code](https://github.com/JuliaOpt/MathOptInterface.jl)). MathOptInterface defines an API that solvers
+Beneath JuMP, there is an abstraction layer called MathOptInterface ([source code](https://github.com/jump-dev/MathOptInterface.jl)). MathOptInterface defines an API that solvers
 should implement so that they can be used by JuMP, handles the automatic
 reformulation of problems via _bridges_, and has a large infrastructure for
 automatically testing solvers.
@@ -17,4 +17,4 @@ solvers, which are often written in C or C++, and implement the API defined by
 MathOptInterface.
 
 A non-exhaustive list of solvers available through JuMP is available in the
-[JuMP documentation](https://www.juliaopt.org/JuMP.jl/stable/installation/).
+[JuMP documentation](https://jump.dev/JuMP.jl/stable/installation/#Getting-Solvers-1).