add a small error message if an invalid kind was passed to jointplot
add a small error message if an invalid kind was passed to jointplot

lukauskas/seaborn,huongttlan/seaborn,cwu2011/seaborn,dotsdl/seaborn,dhimmel/seaborn,uhjish/seaborn,kyleam/seaborn,dimarkov/seaborn,tim777z/seaborn,wrobstory/seaborn,sauliusl/seaborn,drewokane/seaborn,anntzer/seaborn,ashhher3/seaborn,lukauskas/seaborn,clarkfitzg/seaborn,jat255/seaborn,q1ang/seaborn,Guokr1991/seaborn,arokem/seaborn,nileracecrew/seaborn,phobson/seaborn,mclevey/seaborn,parantapa/seaborn,mwaskom/seaborn,muku42/seaborn,mia1rab/seaborn,bsipocz/seaborn,arokem/seaborn,gef756/seaborn,anntzer/seaborn,phobson/seaborn,petebachant/seaborn,jakevdp/seaborn,mwaskom/seaborn,ebothmann/seaborn,aashish24/seaborn,sinhrks/seaborn,Lx37/seaborn,aashish24/seaborn,oesteban/seaborn,olgabot/seaborn,lypzln/seaborn,ischwabacher/seaborn,JWarmenhoven/seaborn