Pin the versions of the remark packages so notifications are sent with new releases, and users can be kept more up to date.

Pin remark and remark-lint versions

https://greenkeeper.io/

https://greenkeeper.io/

*   Update `remark` to 5.1.0;
*   Update `remark-lint` to 4.1.0;
*   Update `eslint`, `eslint-config-airbnb-base`
*   Use `unified-engine-atom` to deal with processing,
    this adds support for `.remarkignore` files, local remark-lint
    configuration files.

Closes GH-71 -  `remark-lint` specified in `.remarkrc` or
`package.json` files now precedes over the packaged `remark-lint`.

Closes GH-93 - Update `remark`;

Closes GH-92 - Update `remark-lint`;

Closes GH-76, closes GH-83 - Using `unified-engine`, which comes with
pretty JSON errors.