Fix photo & camera permission management (#140)

* Check photo & camera perms and alert the user if not available (close #64)

- Adds perms checks with a prompt to update settings if needed
- Moves initial access of photos in the composer so that the initial prompt
  occurs at an intuitive time.

* Add react-native-permissions test mock

* Fix issue causing multiple access requests

* Use longer var names

* Update podfile.lock

* Lint fix

* Move photo perm request in composer to the gallery btn instead of when the carousel is opened

jest/jestSetup.js

@@ -55,3 +55,7 @@ jest.mock('@segment/analytics-react-native', () => ({
     flush: jest.fn(),
   }),
 }))
+
+jest.mock('react-native-permissions', () =>
+  require('react-native-permissions/mock'),
+)