Use $window.attachEvent instead of $window.addEventListener on IE8

[flocca]

This is a fix to make localStorage work properly on IE8.

window.addEventListener doesn't exists in IE8, use window.attachEvent instead.

https://developer.mozilla.org/en-US/docs/Web/API/EventTarget.addEventListener

[gsklee]

Hi @flocca, thanks for the PR! Unfortunately I have no intention to support nonstandard legacy methods, so the only way I can accept it is if you can change L94 to the following or something similar:

'localStorage' === storageType && $window.addEventListener && $window.addEventListener('storage', function(event) {

This should make the module working properly in IE8 except the extra benefit of sync'ing between tabs.

[blowsie]

Am I right in thinking ngstorage supports Angular 1.2 but not IE8?