Documentation for several rules

Added documentation for the following rules:

* `complexity`
* `curly`
* `dot-notation`
* `guard-for-in`
* `max-len`
* `max-params`
* `new-parens`
* `no-alert`

Updated documentation (styling, linking) for the following rules:

* `no-comma-dangle`
* `camelcase`
* `no-plusplus`

I've also created a wiki document for documenting rules that need documentation. Document.

https://github.com/nzakas/eslint/wiki/Rules-Without-Documentation