Update axios dependency

[stefansundin]

Fixes #111.

Even if #112 is eventually ready to merge, I would prefer if this minor upgrade was released first so that users on older nodejs versions can benefit.

$ npm run test

> cloudconvert@2.3.6 test
> mocha --require esm tests/unit



  JobsResource
    all()
      ✓ should fetch all jobs
    get()
      ✓ should fetch a job by id
    create()
      ✓ should send the create request
    delete()
      ✓ should send the delete request
    getExportUrls()
      ✓ should extract the export URLs

  SignedUrlResource
    create()
      ✓ should create a signed URL

  TasksResource
    all()
      ✓ should fetch all tasks
    get()
      ✓ should fetch a task by id
    create()
      ✓ should send the create request
    delete()
      ✓ should send the delete request
    upload()
      ✓ should send the upload request

  UsersResource
    me()
      ✓ should fetch the current user

  WebhooksResource
    verify()
      ✓ should verify the payload


  13 passing (63ms)


$ npm run test-integration

> cloudconvert@2.3.6 test-integration
> mocha --require esm tests/integration



  JobsResource
    create()
      ✓ test upload and download files (5180ms)
    subscribeEvent()
      ✓ test listening for finished event (3215ms)

  TasksResource
    upload()
      ✓ uploads input.png (3352ms)

  UsersResource
    me()
{
  id: 37116784,
  username: 'CloudConvert-OpenSource',
  email: 'support@cloudconvert.com',
  created_at: '2019-05-28T18:22:10+00:00',
  credits: 1000,
  paying: false,
  task_region: null,
  links: { self: 'https://api.sandbox.cloudconvert.com/v2/users/37116784' }
}
      ✓ should fetch the current user (526ms)


  4 passing (12s)

[josiasmontag]

Thanks.