Compilation instructions are incomplete

Hi!

Can you please take a look at the readme and update it ?
I just tried to compile but there is no "buildscript" that I could execute. I managed to get the compiler running using
```bash
cd planner/popf && cmake CMakeLists.txt && make -j 8
```
that created a `popf`-binary but there is no popf-clp binary to execute.

I could also write this down in a pull request if needed.