Update README.md

Author: MartinOtter

README.md

@@ -1,5 +1,8 @@
 # Modia.jl
 
+Modia is **outdated** and should not be used. The package is currently redesigned. 
+For more details, see ModiaSim](https://modiasim.github.io/docs/).
+
 [![Travis](https://travis-ci.org/ModiaSim/Modia.jl.svg?branch=master)](https://travis-ci.org/ModiaSim/Modia.jl)
 [![AppVoyer](https://ci.appveyor.com/api/projects/status/github/ModiaSim/Modia.jl?svg=true)](https://ci.appveyor.com/project/MartinOtter/modia-jl)
 [![codecov.io](http://codecov.io/github/ModiaSim/Modia.jl/coverage.svg?branch=master)](http://codecov.io/github/ModiaSim/Modia.jl?branch=master)