Add JSCS plugin.

Some notes:

1. I used the config I use in Rachet, with a couple of options commented out but left there just in case someone wants to enable them later
2. I'm not very familiar with Gulp so I'm not sure if the gulpfile changes can be simplified
3. With this PR, there are a few JSHint options that can be removed like `indent`, `curly` etc.

/CC @alrra 
Done.