support React Native 0.61; drop React Native 0.59

[brody4hire]

Major (breaking) updates for new 0.x release:

• generate example with React Native 0.61 by default
• remove react-native link step (not needed since React Native 0.60)
• prep: test with generate example for Android only
  (needed to ensure pod install is not run on example in case the module is for Android only)
• do pod install in generated example for iOS
• remove pod install step from manual post-create instructions
• update generated Android view for React Native 0.60(+)
• update template devDependencies for React Native 0.61
• minimum React Native 0.60 in template peerDependencies
• documentation updates
• update documentation for out-of-tree platforms
  (not supported by the generated example)

Tested as follows:

• library module with generated example working on RN 0.61 on Android & iOS
• view module with generated example working on RN 0.61 on Android & iOS
• library module with generated example working on RN 0.60 on Android & iOS
• view module with generated example working on RN 0.60 on Android & iOS

resolves #29
resolves #93
resolves #99
resolves #132
closes #130
closes #192

[brody4hire]

Merged in a squash commit, with the commit message cleaned up in line with the changes listed in the description.

Stryker mutation testing shows a couple of surviving mutants that were introduced, which are very minor:

221. [Survived] StringLiteral
/home/brodybits/create-react-native-module/lib/lib.js:259:30
-                   console.error('pod --version failure, aborting with broken example app');
+                   console.error("");

Ran all tests for this mutant.
227. [Survived] StringLiteral
/home/brodybits/create-react-native-module/lib/lib.js:269:30
-                   console.error('pod install failure, aborting with broken example app');
+                   console.error("");

Ran all tests for this mutant.