Upgrade to lodash v4 (#660)

* npm install lodash-2

Someone handily published a lodash-2 v4.17.4 - it is exactly the same as lodash v4.17.4, so it is safe to use during the migration.

* use lodash-2 in tests

* update tests to split utils vs lodash

* remove Utils.nextTick usage

Utils.nextTick with a single argument is the same as process.nextTick

* lowercase utils

Because it seems that this is the coding style in this repo

* upgrade lodash in grunt/*

* keep lodash-2 as a dev dep for now

* use lodash-2 in scripts

* use snakeCase from utils

It was a mistake in my previous commit to not update this usage

* fix naming gruntUtils vs utils

As all three - gruntUtils, utils and lodash (_) are getting passed into templates, it makes sense to keep the naming consistent

* fix naming gruntUtils vs utils

As all three - gruntUtils, utils and lodash (_) are getting passed into templates, it makes sense to keep the naming consistent

* split utils vs lodash in scripts/generate

Also use lodash-2 where it is easy to do so

* use utils.get until lodash upgrade

* remove lodash.isempty; lodash-2 now used in prod (in src/lib/apis/ code)

* unbundle lodash from utils

* upgrade to lodash 4

* remove lodash.get and lodash.trimEnd

* clean out unused code

* clean out unused code

* fix a breaking change listed under "notable changes" rather than under "breaking changes"...

test/integration/yaml_suite/client_manager.js

@@ -9,7 +9,7 @@ if (BROWSER) {
   es = require('../../../src/elasticsearch');
 }
 
-var _ = require('../../../src/lib/utils');
+var _ = require('lodash');
 var path = require('path');
 var fs = require('fs');
 var fromRoot = _.bindKey(path, 'join', require('find-root')(__dirname));
@@ -130,7 +130,7 @@ module.exports = {
         ]);
       };
 
-      _.nextTick(cb);
+      process.nextTick(cb);
     }
   },
   get: function () {