Bug correction with hamburger status stored in a cookie

I didn't think in some behaviours you hilighted in this issue https://github.com/tmos/greeder/issues/112

So, with this Pull Request, it should be ok I think. I tested it, including some strange behaviors, responsiveness and not, toggling between responsive and not, and all was working in my tests.

The default state for folders is still to be unfolded. I thought it was the default state before my changes, but apparently it's not the case. Tell me and I'll change it.