Make local storage work properly

It was re-initializing over itself. Also make it support a query from a
string key.
Record the last ports successfully used by a device.
Merge branch 'mvp' of github.com:tidepool-org/chrome-uploader into mvp
Make local store testing work now that we need to call init.
Merge branch 'mvp' of github.com:tidepool-org/chrome-uploader into mvp
use a longer variable name
Merge pull request #43 from tidepool-org/kjq/fixStorage

Record the last successful upload port and use it