Stefan add readme files

examples/CoolingHalo/README

+;
+;To make the initial conditions we distribute gas particles randomly in a cube
+;with a side length twice that of the virial radius. The density profile
+;of the gas is proportional to r^(-2) where r is the distance from the centre
+;of the cube. 
+;
+;The parameter v_rot (in makeIC.py and cooling.yml) sets the circular velocity
+;of the halo, and by extension, the viral radius, viral mass, and the 
+;internal energy of the gas such that hydrostatic equilibrium is achieved.
+;
+;While the system is initially in hydrostatic equilibrium, the cooling of the
+;gas means that the halo will collapse.
+;
+;To run this example, make such that the code is compiled with either the
+;isothermal potential or softened isothermal potential, and 'const_lambda' 
+;cooling, set in src/const.h. In
+;the latter case, a (small) value of epsilon needs to be set in cooling.yml.
+;0.1 kpc should work well.
+;
+;The plotting scripts produce a plot of the density, internal energy and radial
+;velocity profile for each snapshot. test_energy_conservation.py shows the 
+;evolution of energy with time. These can be used to check if the example
+;has run properly.
+;
+;
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