[+] Added instructions for assembly and testing.

README.md

 # python-cellframe
 
+## Build and Run tests:
+```
+git clone https://gitlab.demlabs.net/cellframe/python-cellframe.git
+cd python-cellframe
+git submodule update --init
+git submodule foreach git submodule update --init
+mkdir build
+cd build
+cmake ../
+make
+cp ../test/main_test.py ./
+python3.7 main_test.py
+```
+