Changes to optimi.py and kern.py to allow for tying (tieing?) parameters. 
Changes to optimi.py and kern.py to allow for tying (tieing?) parameters. 

TianpeiLuke/GPmat,SheffieldML/GPmat,SheffieldML/GPmat,SheffieldML/GPmat,TianpeiLuke/GPmat,TianpeiLuke/GPmat,TianpeiLuke/GPmat,SheffieldML/GPmat,SheffieldML/GPmat,TianpeiLuke/GPmat,TianpeiLuke/GPmat,SheffieldML/GPmat