chore(package.json): require newer dart2jaas

This helps with caching dart2jaas output.

Ref: https://github.com/jbdeboer/dart2jsaas/commit/7e306509e47f8cc8ec9e431527fd1ccb5863576f
Merge pull request #25 from chirayuk/master

chore(package.json): require newer dart2jaas