Cocoapods complaining about requiring higher minimum deployment target

[rcagantas]

    [!] CocoaPods could not find compatible versions for pod "schedule_notifications":
      In Podfile:
        schedule_notifications (from `.symlinks/plugins/schedule_notifications/ios`)
    
    Specs satisfying the `schedule_notifications (from `.symlinks/plugins/schedule_notifications/ios`)` dependency were found, but they required a higher minimum deployment target.
...
    [!] Automatically assigning platform `ios` with version `8.0` on target `Runner` because no platform was specified. Please specify a platform for this target in your Podfile. See `https://guides.cocoapods.org/syntax/podfile.html#platform`.

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel beta, v0.5.1, on Mac OS X 10.13.5 17F77, locale en-US)
[✓] Android toolchain - develop for Android devices (Android SDK 28.0.0)
[✓] iOS toolchain - develop for iOS devices (Xcode 9.4.1)