feat: compile to ES5 for publishing (#50)

### Summary

Fixes #49

Author: Jukkish

.eslintignore

@@ -1 +1,2 @@
 flow-typed/
+build/

.gitignore

@@ -1,3 +1,4 @@
 node_modules
 *.log
 .eslintcache
+build

package.json

@@ -2,13 +2,14 @@
   "name": "react-native-testing-library",
   "version": "1.4.0",
   "description": "Simple React Native testing utilities helping you write better tests with less effort",
-  "main": "src/index.js",
+  "main": "build/index.js",
   "typings": "./typings/index.d.ts",
   "repository": "[email protected]:callstack/react-native-testing-library.git",
   "author": "Michał Pierzchała <[email protected]>",
   "license": "MIT",
   "private": false,
   "devDependencies": {
+    "@babel/cli": "^7.1.2",
     "@babel/core": "^7.1.2",
     "@babel/runtime": "^7.1.2",
     "@callstack/eslint-config": "^3.0.0",
@@ -21,6 +22,7 @@
     "dedent": "^0.7.0",
     "eslint": "^5.6.1",
     "flow-bin": "^0.86.0",
+    "flow-copy-source": "^2.0.2",
     "jest": "^23.6.0",
     "metro-react-native-babel-preset": "^0.49.0",
     "react": "16.6.1",
@@ -42,7 +44,10 @@
     "flow-check": "flow check",
     "typescript-check": "tsc --noEmit --skipLibCheck --jsx react ./typings/__tests__/*",
     "lint": "eslint src --cache",
-    "release": "release-it"
+    "release": "release-it",
+    "prepublish": "yarn build && yarn copy-flowtypes",
+    "copy-flowtypes": "flow-copy-source --ignore __tests__/*.js src build",
+    "build": "rm -rf build; babel src --out-dir build --presets=module:metro-react-native-babel-preset  --ignore 'src/__tests__/*'"
   },
   "jest": {
     "preset": "react-native"

src/__tests__/renderRNComponents.test.js

@@ -26,7 +26,7 @@ class RNComponents extends React.Component<*> {
               <Text>t2</Text>
               <Text>t3</Text>
             </TouchableOpacity>
-            <ActivityIndicator show />
+            <ActivityIndicator />
           </ScrollView>
         </Modal>
       </View>