fine-tuned jscs rules

Hi @paulrouget,

could you review these changes? I tried to follow your style as much as possible and fine-tuned the `.jscsrc` accordingly. It worked very well with just a few changes.

I do _not_ made a decision about disallowing/requiring trailing commas and didn't set a maximum line length.

I would like to require [`requireSpaceBeforeObjectValues`](https://github.com/jscs-dev/node-jscs#requirespacebeforeobjectvalues) in the future, but it looks like there is a bug with `esnext` enabled: https://github.com/jscs-dev/node-jscs/issues/840.