added Elser demo

demos/Elser_RRR.py

+import pdb
+import SetProxPythonPath
+from proxtoolbox.experiments.phase.Elser_Experiment import Elser_Experiment
+
+Elser = Elser_Experiment(Atoms=200, category='E', algorithm='RRR', lambda_0=0.95, lambda_max=0.95, anim=True)
+Elser.run()
+Elser.show()