Don't let localStorage/sessionStorage setItem throw errors in Safari Private Browsing Mode

localstorage-safari-private-shim.js

// Safari, in Private Browsing Mode, looks like it supports localStorage but all calls to setItem
// throw QuotaExceededError. We're going to detect this and just silently drop any calls to setItem
// to avoid the entire page breaking, without having to do a check at each usage of Storage.
(function(){
	if (typeof localStorage === 'object') {
		try {
			localStorage.setItem('localStorage', 1);
			localStorage.removeItem('localStorage');
		} catch (e) {
			Storage.prototype._setItem = Storage.prototype.setItem;
			Storage.prototype.setItem = function() {};
		}
	}
})();