First release: 0.1.0, 0.2.0, 0.3.0

[yuki24]

User should be able to:

0.1.0

• [x] ~#2: User can initialize the gem with rails g notifier:initialize~ done by rails g pushing:notifier
• [x] #3: User can generate a notifier with e.g. rails g pushing:notifier UserNotifier new_notification
• [x] #4: User can capture client error responses from APNs with rescue_with Fourseam::ApnDeliveryError
• [x] #5: User can capture client error responses from FCMs with rescue_with Fourseam::FcmDeliveryError
• [x] #6: User can observe a response with an Observer
• [x] #12: User can override APN's environment on a delivery basis
• [x] #13: User can override headers for an APN request
• [x] #14: User can use the fcm gem as an adapter
• [x] User can use the lowdown gem as an adapter
• [x] User can use symbols anywhere
• [x] Update the Configuration section in the README

0.2.0

• [x] #8: User can use other helpers
• [x] #9: User can use url helpers
• [x] #16: User can use see logs for APNs environment
• [ ] Update README

0.3.0

• [ ] #7: User can pass in adapter options with e.g. config.apn.adapter_options = {...}
• [x] #10: User can use configure default url options
• [x] #11: User can use configure asset host
• [ ] #15: User can generate a test on rails g pushing:notifier ...
• [ ] #17: User can see logs for APNs request headers
• [ ] #18: User can use a doctor command that tests to help make sure APNs or FCM is configured right
• [ ] User can see a warning if the JSON payload for APNs exceeds 4KB
• [ ] User can see notification previews
• [ ] Update README