Change 'print' by 'return' in main

[iribirii]

Maybe this was unnecessary or there is a better way of doing it, but I use this module inside my scripts to calculate the rmsd between hundreds of pairs of molecules and I need to collected the rmsd values in a matrix.

So I changed the last two print in the main function by return so the results can be collected and used in those scripts when the main function is called as 'rmsd.main(file1,file2,--options...)' from the module.

e.g.

for i in range(n_files):
    for j in range(i+1,n_files):
        results[i,j] = rmsd.main([str(files[i]),str(files[j]),'-e'])