Improves styles and scale of the minimap to get closer of the ST one

The changes includes using the Redacted font to render the minimap editor.

![Minimap with redacted font](https://github-camo.global.ssl.fastly.net/3efd3934dd81a9b2eedc4df002ce2332604c8722/687474703a2f2f692e696d6775722e636f6d2f6267616c4131762e706e67)

See  fundon/atom-minimap#5 for the original issue