perturbed list generation

[hayatehirai]

Hello,

Thank you for the great code!
Through working with it, I have noticed two points to be fixed in relation to randomized ordered list generation.

randomize.jl line 30
sort!(cpd_masses, by= x->x[2], rev=true)
This will sort compounds in descending order of molecular mass.

randomize.jl line 56

i,j = rand(1:length(tuples),2) ## 2 random indices 
if i > j
	i,j = j,i
end

By adding the constraint, the tendency for compounds to be ordered by molecular mass is maintained after 10,000 exchange operations. Although Handorf et al. 2008 did not describe the algorithm for this part in detail, it seems that they added the constraint.

Thank you!
Hayate