Remove najax from default set of sandbox globals.

* Recent versions of ember-data (3.12+) will automatically use
  `ember-fetch` (or global `fetch`) if present, and does not need
  special logic around `najax`
* New applications (as of [email protected]) include `ember-fetch` by
  default, and do **not** include jQuery by default. Considering that
  `najax` is a `jQuery.ajax` emulation API, I think this library should
  avoid exposing it.
* `najax` (as a dependency of this library) is difficult for the host
  application to control (e.g. get their own version), and would be
  better if they provided it themselves (via `buildSandboxGlobals` API)
* Providing backwards compatibility is **very** easy (add `najax:
  require('najax')` via `buildSandboxGlobals`)
* It seems better to "follow a spec" (suggesting `fetch` usage)

For applications that still need `najax` (for example, if they are using
an older ember-data version), they can do (example uses new
`buildSandboxGlobals` API):

```js
const najax = require('najax');

let fastboot = new FastBoot({
  distPath: 'some/path/to/dist',
  buildSandboxGlobals(globals) {
    return Object.assign({}, globals, {
      najax,
    });
  }
});
```

package.json

@@ -28,7 +28,6 @@
     "chalk": "^2.4.2",
     "cookie": "^0.4.0",
     "debug": "^4.1.1",
-    "najax": "^1.0.4",
     "resolve": "^1.12.0",
     "simple-dom": "^1.4.0",
     "source-map-support": "^0.5.13"

src/ember-app.js

@@ -5,7 +5,6 @@ const vm = require('vm');
 const path = require('path');
 const chalk = require('chalk');
 
-const najax = require('najax');
 const SimpleDOM = require('simple-dom');
 const resolve = require('resolve');
 const debug = require('debug')('fastboot:ember-app');
@@ -95,7 +94,6 @@ class EmberApp {
     // add any additional user provided variables or override the default globals in the sandbox
     let globals = Object.assign(
       {
-        najax,
         FastBoot: {
           require: sandboxRequire,
           config: fastbootConfig,

test/fastboot-test.js

@@ -174,7 +174,6 @@ describe('FastBoot', function() {
       distPath: fixture('custom-sandbox'),
       sandboxGlobals: {
         foo: 5,
-        najax: 'undefined',
         myVar: 'undefined',
       },
     });
@@ -184,7 +183,6 @@ describe('FastBoot', function() {
       .then(r => r.html())
       .then(html => {
         expect(html).to.match(/foo from sandbox: 5/);
-        expect(html).to.match(/najax in sandbox: undefined/);
       });
   });
 
@@ -261,7 +259,6 @@ describe('FastBoot', function() {
       distPath: fixture('basic-app'),
       sandboxGlobals: {
         foo: 5,
-        najax: 'undefined',
         myVar: 'undefined',
       },
     });
@@ -275,7 +272,6 @@ describe('FastBoot', function() {
       .then(r => r.html())
       .then(html => {
         expect(html).to.match(/foo from sandbox: 5/);
-        expect(html).to.match(/najax in sandbox: undefined/);
       });
 
     function hotReloadApp() {

yarn.lock

@@ -3119,11 +3119,6 @@ [email protected]:
     editions "^1.1.1"
     textextensions "1 || 2"
 
-jquery-deferred@^0.3.0:
-  version "0.3.1"
-  resolved "https://registry.yarnpkg.com/jquery-deferred/-/jquery-deferred-0.3.1.tgz#596eca1caaff54f61b110962b23cafea74c35355"
-  integrity sha1-WW7KHKr/VPYbEQlisjyv6nTDU1U=
-
 jquery@^3.3.1:
   version "3.4.1"
   resolved "https://registry.yarnpkg.com/jquery/-/jquery-3.4.1.tgz#714f1f8d9dde4bdfa55764ba37ef214630d80ef2"
@@ -3287,11 +3282,6 @@ locate-path@^5.0.0:
   dependencies:
     p-locate "^4.1.0"
 
-lodash.defaultsdeep@^4.6.0:
-  version "4.6.1"
-  resolved "https://registry.yarnpkg.com/lodash.defaultsdeep/-/lodash.defaultsdeep-4.6.1.tgz#512e9bd721d272d94e3d3a63653fa17516741ca6"
-  integrity sha512-3j8wdDzYuWO3lM3Reg03MuQR957t287Rpcxp1njpEa8oDrikb+FwGdW3n+FELh/A6qib6yPit0j/pv9G/yeAqA==
-
 lodash.find@^4.6.0:
   version "4.6.0"
   resolved "https://registry.yarnpkg.com/lodash.find/-/lodash.find-4.6.0.tgz#cb0704d47ab71789ffa0de8b97dd926fb88b13b1"
@@ -3610,15 +3600,6 @@ mz@^2.4.0:
     object-assign "^4.0.1"
     thenify-all "^1.0.0"
 
-najax@^1.0.4:
-  version "1.0.4"
-  resolved "https://registry.yarnpkg.com/najax/-/najax-1.0.4.tgz#63fd8dbf15d18f24dc895b3a16fec66c136b8084"
-  integrity sha512-wsSacA+RkgY1wxRxXCT3tdqzmamEv9PLeoV/ub9SlLf2RngbPMSqc3A7H35XJDfURC0twMmZsnPdsYPkuuFSVg==
-  dependencies:
-    jquery-deferred "^0.3.0"
-    lodash.defaultsdeep "^4.6.0"
-    qs "^6.2.0"
-
 natural-compare@^1.4.0:
   version "1.4.0"
   resolved "https://registry.yarnpkg.com/natural-compare/-/natural-compare-1.4.0.tgz#4abebfeed7541f2c27acfb29bdbbd15c8d5ba4f7"
@@ -4145,11 +4126,6 @@ [email protected]:
   resolved "https://registry.yarnpkg.com/qs/-/qs-6.7.0.tgz#41dc1a015e3d581f1621776be31afb2876a9b1bc"
   integrity sha512-VCdBRNFTX1fyE7Nb6FYoURo/SPe62QCaAyzJvUjwRaIsc+NePBEniHlvxFmmX56+HZphIGtV0XeCirBtpDrTyQ==
 
-qs@^6.2.0:
-  version "6.9.0"
-  resolved "https://registry.yarnpkg.com/qs/-/qs-6.9.0.tgz#d1297e2a049c53119cb49cca366adbbacc80b409"
-  integrity sha512-27RP4UotQORTpmNQDX8BHPukOnBP3p1uUJY5UnDhaJB+rMt9iMsok724XL+UHU23bEFOHRMQ2ZhI99qOWUMGFA==
-
 quick-temp@^0.1.3, quick-temp@^0.1.5:
   version "0.1.8"
   resolved "https://registry.yarnpkg.com/quick-temp/-/quick-temp-0.1.8.tgz#bab02a242ab8fb0dd758a3c9776b32f9a5d94408"