Regressions: fix for Gaussian03/m1b1.out

I recently downloaded all the NIST CCCBDB output files (a lot of data) and starting parsing them with cclib. There are some errors, and this a fix for one I already added to the regression suite -- involving '****' in the output file. Since this signifies numerical problems, I made cclib convert the string to numpy.nan in this case, which seems somewhat reasnoable. I did this in Logfile.float() so that it's a bit more general and should fix similar problems in other cases.

FTR, I have been communicating with Russel Johnson from NIST and have permission to make these files public, with appropriate attribution (will add special notes as needed).