Remove co.wrap usage in favor of using async/await directly.

Used codemod to do the conversion:

```
npx jscodeshift --transform https://raw.githubusercontent.com/albinekb/co-to-async/master/codemod.js path/to/files/*.js works
```

Author: Robert Jackson

.eslintrc.js

@@ -7,7 +7,7 @@ module.exports = {
   ],
   parserOptions: {
     sourceType: 'script',
-    ecmaVersion: 2015
+    ecmaVersion: 2017
   },
   env: {
     browser: false,

commands/index.js

@@ -4,7 +4,6 @@
 const VersionChecker = require('ember-cli-version-checker');
 
 const chalk = require('chalk');
-const co = require('co');
 const fs = require('fs');
 const mkdirp = require('mkdirp');
 const path = require('path');
@@ -47,7 +46,7 @@ const SHARED = {
     return configPath;
   },
 
-  _setFeature: co.wrap(function *(name, value) {
+  _setFeature: async function (name, value) {
     let feature = FEATURES[name];
 
     if (feature === undefined) {
@@ -63,7 +62,7 @@ const SHARED = {
     }
 
     if (typeof feature.callback === 'function') {
-      yield feature.callback(this.project, value);
+      await feature.callback(this.project, value);
     }
 
     let config = {};
@@ -81,7 +80,7 @@ const SHARED = {
     let state = value ? 'Enabled' : 'Disabled';
 
     console.log(chalk.green(`${state} ${chalk.bold(name)}. Be sure to commit ${chalk.underline('config/optional-features.json')} to source control!`));
-  })
+  }
 };
 
 const USAGE = Object.assign({

features/application-template-wrapper.js

@@ -2,7 +2,6 @@
 'use strict';
 
 const chalk = require('chalk');
-const co = require('co');
 const fs = require('fs');
 const inquirer = require('inquirer');
 const p = require('util.promisify');
@@ -14,7 +13,7 @@ module.exports = {
   url: 'https://github.com/emberjs/rfcs/pull/280',
   default: true,
   since: '3.1.0',
-  callback: co.wrap(function *(project, value) {
+  callback: async function (project, value) {
     if (value !== false) {
       return;
     }
@@ -36,7 +35,7 @@ module.exports = {
     let absolutePath = path.join(root, templatePath);
 
     try {
-      originalContent = yield p(fs.readFile)(absolutePath, { encoding: 'UTF-8' });
+      originalContent = await p(fs.readFile)(absolutePath, { encoding: 'UTF-8' });
     } catch(err) {
       if (err.code === 'ENOENT') {
         return;
@@ -63,7 +62,7 @@ module.exports = {
       To be very conservative, I could add the \`<div class="ember-view">\` wrapper to your application.hbs. (You can always remove it later.)
     `);
 
-    let response = yield inquirer.prompt({
+    let response = await inquirer.prompt({
       type: 'confirm',
       name: 'shouldRewrite',
       message: 'Would you like me to do that for you?',
@@ -102,9 +101,9 @@ module.exports = {
 
       console.log(`  ${chalk.yellow('overwrite')} ${templatePath}`);
 
-      yield p(fs.writeFile)(templatePath, content.join('\n'), { encoding: 'UTF-8' });
+      await p(fs.writeFile)(templatePath, content.join('\n'), { encoding: 'UTF-8' });
 
       console.log();
     }
-  })
+  }
 };

features/template-only-glimmer-components.js

@@ -2,7 +2,6 @@
 'use strict';
 
 const chalk = require('chalk');
-const co = require('co');
 const fs = require('fs');
 const inquirer = require('inquirer');
 const glob = require('glob');
@@ -26,7 +25,7 @@ module.exports = {
   url: 'https://github.com/emberjs/rfcs/pull/278',
   default: false,
   since: '3.1.0',
-  callback: co.wrap(function *(project, value) {
+  callback: async function (project, value) {
     if (value !== true) {
       return;
     }
@@ -54,7 +53,7 @@ module.exports = {
 
     // Handle "Classic" layout
     let templatesRoot = path.join(root, 'app/templates/components');
-    let templateCandidates = yield p(glob)('**/*.hbs', { cwd: templatesRoot });
+    let templateCandidates = await p(glob)('**/*.hbs', { cwd: templatesRoot });
 
     templateCandidates.forEach(template => {
       let templatePath = path.join('app/templates/components', template);
@@ -72,7 +71,7 @@ module.exports = {
     // Handle "Pods" layout without prefix
 
     let componentsRoot = path.join(root, 'app/components');
-    templateCandidates = yield p(glob)('**/template.hbs', { cwd: componentsRoot });
+    templateCandidates = await p(glob)('**/template.hbs', { cwd: componentsRoot });
 
     templateCandidates.forEach(template => {
       let templatePath = path.join('app/components', template);
@@ -90,7 +89,7 @@ module.exports = {
     // Handle "Pods" layout *with* prefix
 
     componentsRoot = path.join(root, `app/${podsFolder}/components`);
-    templateCandidates = yield p(glob)('**/template.hbs', { cwd: componentsRoot });
+    templateCandidates = await p(glob)('**/template.hbs', { cwd: componentsRoot });
 
     templateCandidates.forEach(template => {
       let templatePath = path.join(`app/${podsFolder}/components`, template);
@@ -138,7 +137,7 @@ module.exports = {
       `);
     }
 
-    let response = yield inquirer.prompt({
+    let response = await inquirer.prompt({
       type: 'confirm',
       name: 'shouldGenerate',
       message: 'Would you like me to generate these component files for you?',
@@ -152,11 +151,11 @@ module.exports = {
         let componentPath = components[i];
         console.log(`  ${chalk.green('create')} ${componentPath}`);
         let absolutePath = path.join(project.root, componentPath);
-        yield p(mkdirp)(path.dirname(absolutePath));
-        yield p(fs.writeFile)(absolutePath, ComponentFile, { encoding: 'UTF-8' });
+        await p(mkdirp)(path.dirname(absolutePath));
+        await p(fs.writeFile)(absolutePath, ComponentFile, { encoding: 'UTF-8' });
       }
 
       console.log();
     }
-  })
+  }
 };

package.json

@@ -25,7 +25,6 @@
   },
   "dependencies": {
     "chalk": "^3.0.0",
-    "co": "^4.6.0",
     "ember-cli-version-checker": "^3.1.3",
     "glob": "^7.1.6",
     "inquirer": "^7.0.1",