Run eslint tests with jest

Turns out eslint-tester works with jest (!)

We take advantage of this internally at FB, so we'll do it here too.

Fixes facebook#4328

Author: bgw

Gruntfile.js

@@ -114,7 +114,6 @@ module.exports = function(grunt) {
   ]);
   grunt.registerTask('build:test', [
     'delete-build-modules',
-    'test:eslint-rules',
     'jsx:test',
     'version-check',
     'populist:test',
@@ -133,8 +132,6 @@ module.exports = function(grunt) {
 
   grunt.registerTask('coverage:parse', require('./grunt/tasks/coverage-parse'));
 
-  grunt.registerTask('test:eslint-rules', require('./grunt/tasks/test-eslint-rules'));
-
   grunt.registerTask('test:webdriver:phantomjs', [
     'connect',
     'webdriver-phantomjs',

grunt/tasks/test-eslint-rules.js

@@ -95,7 +95,8 @@
       "/.module-cache/"
     ],
     "testPathDirs": [
-      "<rootDir>/src"
+      "<rootDir>/src",
+      "<rootDir>/eslint-rules"
     ],
     "unmockedModulePathPatterns": [
       ""