Wrong license definition in package.json

NPM defines the license to be given differently than it is currently done: https://docs.npmjs.com/files/package.json#license

Current situation:

`"licenses": {
"type": "(MIT)",
"url": "https://github.com/joypixels/emoji-toolkit/blob/master/LICENSE.md"
},`

Should be like:

`"license" : "MIT"`

The files property can be used to distribute the LICENSE.md file if necessary: https://docs.npmjs.com/files/package.json#files

Why it came up: we have tools to generate the 3rd party component disclosure documents that are crawling all node modules. It's failing with this package because it cannot parse.