removed unnecessary comment
if smallest model coefficient is more negative than maximum model coefficient
is positive, return 2.0*chisq_exception as basis error
hack so that Ebest0 is not set to chisq_exception
actually, make it start negative
sensible way to keep dominant coefficient positive
removed diagnostic print statement
added possibility to pass array of switches to perturb_bases
actually, pass a list of frozen bases
trying to get it to respect positivity of frozen vectors
does not seem to be working