up to 0.0.3.1 - synchronization between instances

Thanks to new permission "storage" added to manifest.json, extension
have now access to synced storage of Chrome. Thanks to this when one
instance of extension will set new value of since (so last time when any
operation was done on Pocket API, what helps to download only
information about articles added after last taging session) all other
will be updated.
Thanks to this if you are using extension on mulpitple machines you
should avoid situation when all your articles are continously tagged.