Ignore all function parameters option

[natelong]

Just whipped up a little patch to allow users to turn off function parameter testing, since it forces a lot of false positives, and isn't a bad practice in and of itself. Here's an example:

function (foo, bar) {
    console.log(bar);
}

You need to have foo declared so you can address bar whether or not you need foo.

Now, if you pass --ignore-all-parameters into the CLI, the unused function will ignore all unused function parameters.

Update after some discussion on earlier pull request

[defunctzombie]

This doesn't address some of the other concerns. Also, please collapse any commits into one before making a feature pull request :)