adds readme.md

readme.md

+Software Requirements:
+======================
+
+CMake [cmake.org](https://cmake.org/):
+* minimum version 3.13
+
+CUDA [developer.nvidia.com/cuda-zone](https://developer.nvidia.com/cuda-zone):
+* Minimum CUDA Version 9.0
+* Minimum Compute Capability 3.0, because of maximal number of Blocks in x direction
+* Recommended Compute Capability 6.0, because of atomics for double precision floating point data (GKS only)
+    
+Paraview [www.paraview.org](https://www.paraview.org/):
+* any version, for example the most recent
+    
+C++ Compiler:
+* with C++11 support, for example gcc6.3 or Visual C++ 14.0
+    
+How to get Virtual Fluids:
+==========================
+
+Option 1: use git
+1. checkout out https://git.irmb.bau.tu-bs.de/VirtualFluids/VirtualFluidsGPU.git with your credentials
+
+Option 2: without git
+1. go to git.irmb.tu-bs.de
+2. Log in with your credentials
+3. click on VirtualFluids/VirtualFluidsGPU
+4. click on the download symbol on the top right and download zip/tar.gz file
+
+How to build Virtual Fluids:
+============================
+
+1. CMake the project
+2. set the output path in targets/apps/LidDrivenCavity/LidDrivenCavity.cpp
+3. build the project ("compile")
+4. run the generated executable (usually in <build directory>/bin/)
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