Improve CircleCI infrastructure (#1173)

* [Example] Get tests passing on ReduxExample and NavigationPlayground

* [CI] Use more vague versioning so we're always up to date

* [CI] Test that the example apps run without error

* [CI] Install the current local version of react-nav before testing

* Fix tabs => spaces in ReduxExample/package.json

* Remove LinkingExample entirely

It's now part of NavigationPlayground.

examples/NavigationPlayground/package.json

@@ -2,10 +2,28 @@
   "name": "NavigationPlayground",
   "version": "0.0.1",
   "private": true,
+  "scripts": {
+    "test": "jest"
+  },
   "dependencies": {
     "react": "16.0.0-alpha.6",
     "react-native": "^0.43.2",
     "react-native-vector-icons": "^4.0.1"
   },
-  "devDependencies": {}
+  "devDependencies": {
+    "babel-jest": "^19.0.0",
+    "jest": "^19.0.2",
+    "react-navigation": "git+https://github.com/react-community/react-navigation.git",
+    "react-test-renderer": "^15.5.4"
+  },
+  "jest": {
+    "preset": "react-native",
+    "setupFiles": [
+      "<rootDir>/../../jest-setup.js"
+    ],
+    "transformIgnorePatterns": [
+      "node_modules/(?!react-native|react-navigation)/",
+      "__exponent"
+    ]
+  }
 }