fix "Warning: Matrix is not positive definite" error

[jsnelgro]

getting this error:

Warning: Matrix is not positive definite 
  In logdet (line 15)
  In mywishpdfln (line 32)
  In simAnneal (line 41)
  In runAnnealBayes (line 40)
  In runFullSims (line 142) 

[jsnelgro]

• possible solution: check if datapoint determinant is positive. If it's not, throw out the data point and move on. (because it's a useless datapoint anyways)