Warn about long run time of init.

Summary:
I, like many before me, had to Google why react-native init appeared to hang the first time I tried it.

It turns out it can just take a really long time, but does not give any warning of this fact.

This patch provides such a warning.
Closes facebook#9406

Differential Revision: D3716357

Pulled By: bestander

fbshipit-source-id: 6a460c881a20b9edb1bd1c8c5df09e5a7e5020ed

react-native-cli/index.js

@@ -102,6 +102,7 @@ if (cli) {
       );
       process.exit(1);
     } else {
+      if (!argv.verbose) console.log('This may take some time...');
       init(commands[1], argv.verbose, argv.version);
     }
     break;
@@ -263,7 +264,7 @@ function checkForVersionArgument() {
     try {
       console.log('react-native: ' + require(REACT_NATIVE_PACKAGE_JSON_PATH()).version);
     } catch (e) {
-      console.log('react-native: n/a - not inside a React Native project directory')
+      console.log('react-native: n/a - not inside a React Native project directory');
     }
     process.exit();
   }