Updating redux-saga to 0.15.3, webpack to v2 and adding yarn

[jportela]

At the time the blog post was created, the redux-saga project was running at version 0.9.5. Over the past year the library changed quite a bit, with some breaking changes, so I updated the example code to work with the most recent version of the library (15.0.3 at the moment). The blog post wasn't updated though, if you want to check the exact version of the example that was working on 0.9.5 check https://github.com/jportela/redux-saga-persistence/tree/0.9.5

The following changes were done:

• Changed from fork to spawn, because we want to keep the process detached
• Added the sagaMiddleware.run(sagas); to the store
• Simplified the Lock system by removing isLocked since the <Task>.isRunning() method provides similar functionality
• Removed the try/catch block in debounceSave because
• Updated webpack from v1 to v2
• Added yarn as the dependency manager