updated readme with Griddle
updated readme with Griddle

fixes #54 and now suggests Griddle for dependencies.
lichblitz/DBFlow,tsdl2013/DBFlow,panzerfahrer/DBFlow,dantman/DBFlow,kaeawc/DBFlow,SeaSoon/DBFlow,sevar83/DBFlow,yoshimaa/DBFlow,pranavlathigara/DBFlow,Raizlabs/DBFlow,pranaypatel512/DBFlow,leasual/DBFlow,cgpllx/DBFlow,mickele/DBFlow,bboyfeiyu/DBFlow,Raizlabs/DBFlow,R4md4c/DBFlow,sujeet-kumar-mehta/DBFlow,hanhailong/DBFlow,janzoner/DBFlow,MyFavoriteFork/DBFlow,mickele/DBFlow