Add iOS function `requestStateForRegion`

iOS: Added the requestStateForRegion function and the corresponding listener didDetermineState.

Android: Improve connect() call handling

• Removes the routine added in PR #21 which was put in place to resolve/reject a Promise only once. However this caused to have an un-handled Promise.
• Adds a new event beaconInitStatus which is triggered when the connect() call was successful or unsuccessful.

Android: Improve error handling

Reject most methods with an error message if the underlying object is not defined becauseconnect() was not called yet or didn't successfully run through.
This avoids generic null-pointer exceptions.

Note: The method disconnect was checking whether the object was defined, but just quit silently. Now it is also rejecting the promise.

Upgrade gradle build tools to Version 25

The update of the gradle build tools makes react-native-kontaktio compatible with react-native v0.55.4.

Compatibility with RN version 0.48 and up

Now compatible with RN 0.48 and up

Tested with RN version 0.49.3

Compatibility with RN version 0.47

The package is now compatible with RN 0.47 and up while maintaining downwards compatibility.

iOS version, improvements and Android eddystone support

iOS

• discovery, ranging and monitoring possible

Android

• Eddystone support
• New method getBeaconRegions() to get all regions which are set to scan.
• Rename init() to connect() and improve functionality so that disconnect() is the opposite action.
• Several bug fixes

Cross-platform

• Updated example apps
• Improved documentation (start-up documentation tested for react-native versions below and after 0.40.0)

New methods and bug fixes

• Add methods isConnected and isScanned.
• Fix issue when calling restartScan in which proximityManager is not yet connected but proximityManager.startScanning is called.
• Fix bug in Example: When more than one beacon are currently in Range and one of them disappeared, no beacons were shown anymore and the app threw an error. This bug is fixed.

Complete rewrite of Android version

• Updates Kontakt.io SDK version to 3.2.3.
• With this update come major improvements and changes in the API which are reflected in the API of this module
  • API is configurable
  • API offers many levels of interaction with incoming beacon signals
• Monitoring is possible now
• Multiple regions may be ranged/monitored simultaneously
• All functions are now promised based.
• Module got safe by adding try-catch blocks around all function calls and adding sensible error messages or exposing the error messages of the Kontakt.io SDK where necessary.
• Under the hood the Android Java code got a much better structure and is much better maintainable.
• Groundwork for Eddystone support is made so that integration in the near future should be easy.