Add a test case for jQuery with mixed-case attributes.
Add a test case for jQuery with mixed-case attributes.

Closes #340.

medikoo/jsdom,Sebmaster/jsdom,Sebmaster/jsdom,danieljoppi/jsdom,selam/jsdom,fiftin/jsdom,sebmck/jsdom,nicolashenry/jsdom,kevinold/jsdom,lcstore/jsdom,medikoo/jsdom,kesla/jsdom,evanlucas/jsdom,kittens/jsdom,mbostock/jsdom,zaucy/jsdom,darobin/jsdom,kangax/jsdom,kesla/jsdom,mzgol/jsdom,janusnic/jsdom,tmpvar/jsdom,jeffcarp/jsdom,AshCoolman/jsdom,aduyng/jsdom,robertknight/jsdom,snuggs/jsdom,sebmck/jsdom,evdevgit/jsdom,mzgol/jsdom,kangax/jsdom,Ye-Yong-Chi/jsdom,nicolashenry/jsdom,cpojer/jsdom,janusnic/jsdom,selam/jsdom,danieljoppi/jsdom,zaucy/jsdom,sirbrillig/jsdom,aduyng/jsdom,mzgol/jsdom,vestineo/jsdom,szarouski/jsdom,snuggs/jsdom,AshCoolman/jsdom,Joris-van-der-Wel/jsdom,aduyng/jsdom,beni55/jsdom,dexteryy/jsdom-nogyp,Joris-van-der-Wel/jsdom,vestineo/jsdom,dexteryy/jsdom-nogyp,susaing/jsdom,sirbrillig/jsdom,lcstore/jsdom,AshCoolman/jsdom,darobin/jsdom,beni55/jsdom,papandreou/jsdom,crealogix/jsdom,fiftin/jsdom,robertknight/jsdom,darobin/jsdom,danieljoppi/jsdom,kevinold/jsdom,selam/jsdom,jeffcarp/jsdom,AVGP/jsdom,zaucy/jsdom,szarouski/jsdom,kittens/jsdom,susaing/jsdom,Ye-Yong-Chi/jsdom,evdevgit/jsdom,Sebmaster/jsdom,evanlucas/jsdom,AVGP/jsdom,evanlucas/jsdom,sebmck/jsdom,jeffcarp/jsdom,kesla/jsdom,Ye-Yong-Chi/jsdom,Zirro/jsdom,Zirro/jsdom,vestineo/jsdom,janusnic/jsdom,tmpvar/jsdom,susaing/jsdom,beni55/jsdom,kittens/jsdom,robertknight/jsdom,Joris-van-der-Wel/jsdom,sirbrillig/jsdom,medikoo/jsdom,crealogix/jsdom,lcstore/jsdom,papandreou/jsdom,cpojer/jsdom,nicolashenry/jsdom,kevinold/jsdom,fiftin/jsdom,mbostock/jsdom,szarouski/jsdom,mbostock/jsdom,evdevgit/jsdom,cpojer/jsdom