chrome-storage-sync adapter (work in progress)

I wrote a lawnchair adapter for chrome.storage.sync (only for chrome apps and extensions at the moment). 

Advantages:
* automatically syncs data between a user's chrome browsers
* relatively simple
* like localStorage but better:
* you can do mass reads, mass writes and mass deletes

Disadvantages:
* severe data caps (MAX_WRITE_OPERATIONS_PER_HOUR, MAX_ITEMS, QUOTA_BYTES, MAX_SUSTAINED_WRITE_OPERATIONS_PER_MINUTE)
* most can't be worked around (only QUOTA_BYTES_PER_ITEM really can)
* needs a work around for individual objects (linked-lists maybe?)
* "chrome.storage is not a big truck. It's a series of tubes."

see https://developer.chrome.com/apps/storage.html#sync-properties
for details