Patch String.prototype.trim() to work in all browsers.

It's nice to be able to call " foo ".trim() to get "foo", but this doesn't work in older browsers. Here's a shim so that it does.

// Patch trim function
if (!String.prototype.trim) {
    String.prototype.trim = function () {
        return this.replace(/^\s+|\s+$/g,'');
    };
}

(If you are against overriding String.prototype, you can always use $.trim().)