Fix package.json validation issues

[azisnaufal]

File : https://github.com/scorelab/Stackle/blob/master/stackle_app/package.json

Result from http://package-json-validator.com/

{
  "valid": false,
  "errors": [
    "Missing required field: version"
  ],
  "warnings": [
    "Missing recommended field: description",
    "Missing recommended field: keywords",
    "Missing recommended field: bugs",
    "Missing recommended field: licenses",
    "Missing recommended field: author",
    "Missing recommended field: contributors",
    "Missing recommended field: repository"
  ],
  "recommendations": [
    "Missing optional field: homepage"
  ]
}

Hi! I would like to work on this issue.