Docs: Show what JSCS does on home page

[hzoo]

Clarify being able to null/extend presets #1285.
One would be under the --preset option in http://jscs.info/overview.html#cli.
Another might be a small note under the preset section - I would mention being able to extend presets as well as disable rules and link to the preset section.
So I guess just link to the section about being able to null/extend presets in other places.

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Also I think it would be nice to give an example of what jscs does in the about/home page. config/install info - So maybe an example .jscs config that shows off the common features (preset + extend) + autofix.

[hzoo]

Ok nulling rules was also in #971, so that covers the first suggestion.

[hzoo]

Changed issue to be about the 2nd issue if we want to do something like that.

[markelog]

👍

[qfox]

👍

[hzoo]

Although I guess this could be an issue in the website repo instead?

[markelog]

Yep - https://github.com/jscs-dev/jscs-dev.github.io/issues/24