Update package.json

Good day! Nap looks fantastic, but I couldn't get it working out of the box without adding nib to my project dependencies. This is my first ever contribution on github so if I'm dead wrong let me know :)

Move set nib as dependency from devDependency to prevent error:

Error: /home/jam/workspace/cheetah/views/index.jade:5
    3| 	head
    4| 		title= title
  > 5| 			!= nap.css("all")
    6| 	body
    7| 		.grid-container
    8| 			#product-container

Cannot find module 'nib'
    at Function.Module._resolveFilename (module.js:338:15)
    at Function.Module._load (module.js:280:25)
    at Module.require (module.js:362:17)
    at require (module.js:378:17)
    at Object.module.exports.preprocessors.preprocessors..styl (/home/jam/workspace/cheetah/node_modules/nap/lib/nap.coffee:363:87)
    at preprocess (/home/jam/workspace/cheetah/node_modules/nap/lib/nap.coffee:427:32)
    at preprocessPkg (/home/jam/workspace/cheetah/node_modules/nap/lib/nap.coffee:440:177)
    at Function.module.exports.css (/home/jam/workspace/cheetah/node_modules/nap/lib/nap.coffee:155:13)
    at eval (eval at <anonymous> (/home/jam/workspace/cheetah/node_modules/jade/lib/jade.js:176:8))
    at exports.compile (/home/jam/workspace/cheetah/node_modules/jade/lib/jade.js:181:12)
GET / 500 58ms