Cut the mustard with proxy browsers taken into consideration

mustard-test.js

var hasStorage = (function() {
    try {
        localStorage.setItem("test", "mod" );
        localStorage.removeItem("test");
        return true;
    } catch (exception) {
        // console.info(exception);
        if (exception && exception.name=="QuotaExceededError" && localStorage.length == 0) {
            //private
            return true;
        } else {
            return false;
        }
    }
}());

if( 'querySelector' in document && hasStorage && 'addEventListener' in window ){
//cuts the mustard  
}

Updating the cuts the mustard check to address issues with some proxy browsers (most notably UC Mini) where the original test appears to pass, even though localStorage isn't actually functioning.

The stuff on #8 is to account for private browsing.

I think it can be a little shorter, taking out one of those return true statements if the if statement is inverted. Also, I mentioned http://chrisberkhout.com/blog/localstorage-errors/ for the exception name, but I can't find a list of possible exceptions.

Also, if storage is full (possible, not likely) it would return false as well