CLI: Remove artifact of old stdin implementation
Add link to the Atom editor plugin for JSCS

This change adds a link to the Atom editor plugin.
It's had about ~5.8K downloads so far and may be worth mentioning

Closes gh-571
Improve docs

* Remove duplication for rules disabling in presets

* Use js syntax for js

* Simplify docs a bit
CLI: Only read stdin if there were no files supplied and not in tty mode or '-' supplied as first argument. Fixes #563