Added a few fields to package.json

Changed `repo` to `repository`.
Added `bugs` and `homepage` (even though npm technically resolves them from the `repository` field anyways &mdash; which is probably all moot since `private` is set to true).

Current [package.json validator](http://package-json-validator.com/) output is:
```json
{
  "valid": false,
  "errors": [
    "Type for field repository, was expected to be object, not string"
  ],
  "warnings": [
    "Missing recommended field: keywords",
    "Missing recommended field: contributors"
  ]
}
```

(The "Type for field repository, was expected to be object, not string" feels like an error in the validator, https://github.com/gorillamania/package.json-validator/issues/29)