Add instructions on running the whole thing

RunDemo.md

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+# Running a demo version
+
+As for now, it's possible to take ReCodEx on a test drive on a single Linux 
+machine. To do so, follow these steps:
+
+- Install Python 3.5 and the `python-requests` library
+- Clone and build the broker and worker
+- Launch the testing file server contained in the `tools` directory of the 
+  broker project
+- Launch the broker (run it in the `examples` subdirectory which contains a 
+  working config file)
+- Launch a worker (again, use the `examples` subdirectory as the working 
+  directory)
+- Submit a directory using the `fake_submit.py` script in the `tools` directory 
+  of the worker project
+- Something should be happening now...
+
+Follow the readmes of the projects and headers of the files with helper scripts 
+(tools) if anything is unclear.