Upgrade localforage

Signed-off-by: chatgris <julien@stormz.me>
Adapt code to latest localforage version

see
https://github.com/mozilla/localForage/commit/4c1b8943cdad64598c6f47eba4b2d1ba526d209b

Signed-off-by: chatgris <julien@stormz.me>
Invoke error callback on localforage err

Signed-off-by: chatgris <julien@stormz.me>
Merge pull request #12 from chatgris/upgrade_localforage

Upgrade localforage