Best known clique numbers in readme.md do not match the DIMACS reference

[leowonglaw]

I think that the readme needs to be updated because it's best known clique numbers do not match the DIMACS reference.

For example:

• C1000.9: 67 to 68
• C2000.9: 75 to 80

Thanks for the awesome work

[shah314]

Yes, this work was done several years back, so the best known cliques may have improved (for which the optimum is not known). Thanks.