createObjectStore doesn't support autoIncrement.

[dfbaskin]

The code to create the object store prevents adding an auto increment key:

      versionSchema.stores.forEach(function(store) {
        db.createObjectStore(store.name, { keyPath: store.opts.key });
      });

Reference: https://developer.mozilla.org/en-US/docs/Web/API/IDBDatabase.createObjectStore#Parameters

[alekseykulikov]

Added in 0.2.0: https://github.com/alekseykulikov/treo/blob/master/History.md#020--2014-09-08