Change client.js to use utils.extractParams for params to array mapping

[hoppula]

With previous version of page.js (up to new 1.6.0) Context's params used to be an array-like object, but after this change visionmedia/page.js#205 it's plain object, so the key order can be anything.

We need to change
https://github.com/SC5/cerebellum/blob/master/lib/client.js#L48 to use utils.extractParams like server.js does before updating to page.js 1.6.0.