howto-include.txt: Update example url to most recent one
howto-include.txt: Update example url to most recent one

Previous url was broken, updated to most recent
remotestorage/remotestorage.js,lewisl9029/remotestorage.js,lewisl9029/remotestorage.js,untitaker/remotestorage.js,remotestorage/remotestorage.js,theWebalyst/remotestorage.js,mcanthony/remotestorage.js,remotestorage/remotestorage.js,mcanthony/remotestorage.js,untitaker/remotestorage.js,theWebalyst/remotestorage.js