numberify = function(s) {
            var c = 0;
            return parseFloat(s.replace(/\./g, function() {
                return (c++ === 1) ? '' : '.';
            }));
        }
Static method on `YUI.Env` for parsing a UA string.  Called at instantiation
to populate `Y.UA`.

@static
@method parseUA
@param {String} [subUA=navigator.userAgent] UA string to parse
@return {Object} The Y.UA object