Hotfix: Prevent handler being ARC on iOS before resolving the request

[booker0108]

Summary

To resolve the problem of handler being ARC on iOS [#390 ]

• Create a strong reference in RNPermission.h
• Add a method to store handler in NSDictionary and return a random ID for disposing after use

Test Plan

• Create a memory-consuming app
• Invoke Location permission request
• Old implement might get to a situation that the dialog dismiss itself before user action because of aggressive ARC
• New implementation will not encounter the issue as handler is now stored in a strong reference to prevent ARC

What's required for testing (prerequisites)?

• A bulky app which cause the bug (Release mode only)

What are the steps to reproduce (after prerequisites)?

• Invoke Location permission request

Compatibility

OS	Implemented
iOS	✅
Android	❌ (Not applicable)

Checklist

• I have tested this on a device and a simulator
• I added the documentation in README.md
• I mentioned this change in CHANGELOG.md
• I updated the typed files (TS and Flow)
• I added a sample use of the API in the example project (example/App.js)

[zoontek]

LGTM 👍