v0.0-6
 - added an mafc link for the cloglog link, which permits fitting Weibull
 psychometric functions on a log stimulus axis.  See example(mafc).
v0.0-7
 - added mafc.weib link that is just an alias for mafc.cloglog
 - added mafc.cauchit link
v0.0-8
 - added additional links that include parameters for both upper and lower  
 asymptotes and a function, psyfun.2asym, that is a wrapper for glm and 
 uses the new links to fit a psychometric function with variable lower and 
 upper asymptotes.
v0.0-9
 - added standard error estimates based on the Hessian from last iteration 
 of optim to the output of psyfun.2asym (suggested by Ralph Pirow).