Use >= instead of $\ge$

README.md

 # nest-streaming-module
 
 ## Prerequisites
-* CMake $\ge$ 3.6.0 (https://cmake.org/)
+* CMake >= 3.6.0 (https://cmake.org/)
 * Python 2.7 (https://www.python.org/)
 * Conan (`pip install conan`)
 * NEST: the latest release of NEST does currently not support modules. Thus, a custom version is required that can be found [here](https://github.com/jougs/nest-simulator/tree/feature/custom-recording-backend).