* npksum now supports an expanded set of kernels (including 
  convolution, derivative and integral), which can be selected
  via the 'operator' argument.
* automatic bandwidth searches are now performed when attempting to 
  evaluate on data without bandwidths.
* npsigtest interface brought in line with other functions.
* significance tests can now be performed on npreg outputs.
* added a vignette and faq.
* summary on npconmode now properly retrieves names from bandwidth 
  objects.
* fixed the 6th and 8th order epanechnikov kernels.
* fixed some quietness issues.
* npplot now returns data upon request for conditional densities.
* npreg and npcdens now take the appropriate limits in some 
  pathological cases.
