Add `.editorconfig` file

The addition of the `/.editorconfig` file is made in order to
help us define and maintain consistent coding styles between our
different editors and IDEs.

Ref: http://editorconfig.org/
Add required fields to `package.json`

Add basic fields to the `package.json` file in order to allow `npm`
to install the `server-configs-apache` package.

Note: Even thought the package is not yet published to the `npm`
registry, with these additions, `npm` will be able to install it
just by doing:

    npm install <tarball file>
    npm install <tarball url>
    npm install <folder>

Ref: https://www.npmjs.org/doc/files/package.json.html
     https://www.npmjs.org/doc/cli/npm-install.html
Add configs for TopoJSON files (`.topojson`)

* Serve `.topojson` files compressed and with the `application/json`
  media type (there isn't yet and official or recommended media type).

* Ensure that `.topojson` files aren't served with any of the `HTML`
  document related headers, are not cached, and their specified
  character encoding is `UTF-8`.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Thanks @calvinmetcalf!

Ref: https://github.com/topojson/topojson-specification
     h5bp/server-configs-apache#34

Close h5bp/server-configs-apache#34