CAS numbers for G2

This updated dataset includes 'CAS No.' for 148 small molecules and 14 atoms within G2/97 Test Set. This is important because there are several symmetry labels for molecules and existence of CAS No. in identification will obviously affect the scientific comparisons. All CAS numbers were adopted from https://cccbdb.nist.gov. 'Spin state' is also doublechecked by total energy calculations performed by Pyscf meanwhile, the results are in agreement with previous reports. Further, 'name' has been corrected by IUPAC ID in several cases.dataset.py