Update findAvailablePort to use inquirer

Prompt's dependency winston is causing a warning in the console:

> (node:15613) Warning: Accessing non-existent property 'padLevels' of module exports inside circular dependency

This has been raised as an issue on prompt's GitHub repo [1] but given the last release of prompt was 4 years ago, I think it makes sense to move away to an alternative that's actively maintained.

[1]: flatiron/prompt#199

lib/utils.js

@@ -6,7 +6,7 @@ const getKeypath = require('keypather/get')
 const marked = require('marked')
 const path = require('path')
 const portScanner = require('portscanner')
-const prompt = require('prompt')
+const inquirer = require('inquirer')
 const request = require('sync-request')
 
 // Local dependencies
@@ -86,23 +86,14 @@ exports.findAvailablePort = function (app, callback) {
     } else {
       // Port in use - offer to change to available port
       console.error('ERROR: Port ' + port + ' in use - you may have another prototype running.\n')
-      // Set up prompt settings
-      prompt.colors = false
-      prompt.start()
-      prompt.message = ''
-      prompt.delimiter = ''
 
       // Ask user if they want to change port
-      prompt.get([{
-        name: 'answer',
-        description: 'Change to an available port? (y/n)',
-        required: true,
-        type: 'string',
-        pattern: /y(es)?|no?/i,
-        message: 'Please enter y or n'
-      }], function (err, result) {
-        if (err) { throw err }
-        if (result.answer.match(/y(es)?/i)) {
+      inquirer.prompt([{
+        name: 'changePort',
+        message: 'Change to an available port?',
+        type: 'confirm'
+      }]).then(answers => {
+        if (answers.changePort) {
           // User answers yes
           port = availablePort
           fs.writeFileSync(path.join(__dirname, '/../.port.tmp'), port)

package.json

@@ -35,6 +35,7 @@
     "gulp-nodemon": "^2.5.0",
     "gulp-sass": "^4.0.1",
     "gulp-sourcemaps": "^2.6.0",
+    "inquirer": "^7.1.0",
     "keypather": "^3.0.0",
     "marked": "^0.8.2",
     "notifications-node-client": "^4.7.2",