Run Jest tests with "development" environment (facebook#11612)

Author: gaearon

scripts/jest/preprocessor.js

@@ -1,8 +1,6 @@
 'use strict';
 
-// React's test can only work in NODE_ENV=test because of how things
-// are set up. So we might as well enforce it.
-process.env.NODE_ENV = 'test';
+process.env.NODE_ENV = 'development';
 
 var path = require('path');