CLI: Show npm / yarn output during 'react-native-init' when installing React and Jest

Summary:
I missed this while doing the Yeoman wipeout.

Currently we just print:

    Installing React...
    Installing Jest...

This diff makes it print the output of those commands.

**Test Plan**

Published react-native to Sinopia, ran `react-native init MyApp`, saw the output:

    Installing Jest...
    ⸨░░░░░░░░░░░░░░░⸩ ⠸ normalizeTree: ...

Reviewed By: bestander

Differential Revision: D4286640

fbshipit-source-id: e554f03a4729c2de85eba527f10f4b727de722e4

Author: Martin Konicek

local-cli/init/init.js

@@ -75,21 +75,21 @@ function generateProject(destinationRoot, newProjectName, options) {
 
   if (yarnVersion) {
     console.log('Adding React...');
-    execSync(`yarn add react@${reactVersion}`);
+    execSync(`yarn add react@${reactVersion}`, {stdio: 'inherit'});
   } else {
     console.log('Installing React...');
-    execSync(`npm install react@${reactVersion} --save --save-exact`);
+    execSync(`npm install react@${reactVersion} --save --save-exact`, {stdio: 'inherit'});
   }
   if (!options['skip-jest']) {
     const jestDeps = (
       `jest babel-jest babel-preset-react-native react-test-renderer@${reactVersion}`
     );
     if (yarnVersion) {
       console.log('Adding Jest...');
-      execSync(`yarn add ${jestDeps} --dev --exact`);
+      execSync(`yarn add ${jestDeps} --dev --exact`, {stdio: 'inherit'});
     } else {
       console.log('Installing Jest...');
-      execSync(`npm install ${jestDeps} --save-dev --save-exact`);
+      execSync(`npm install ${jestDeps} --save-dev --save-exact`, {stdio: 'inherit'});
     }
     addJestToPackageJson(destinationRoot);
   }