feat: Adds appveyor build file

[joshwiens]

Adds an appveyor build file to webpack-defaults

• The service has been configured for the org - https://ci.appveyor.com/projects
• The service account has already been configured - https://github.com/webpack-contrib-appveyor
• Teams within contrib have been assigned the proper permissions to access the service.

Output ...

branches:
  only:
    - master

init:
  - git config --global core.autocrlf input

environment:
  matrix:
    - nodejs_version: 7
      webpack_version: 2.2.0
      job_part: test
    - nodejs_version: 6
      webpack_version: 2.2.0
      job_part: test
    - nodejs_version: 4.3
      webpack_version: 2.2.0
      job_part: test

install:
  - ps: Install-Product node $env:nodejs_version x64
  - npm install

build: off

matrix:
  fast_finish: true

before_test:
  - cmd: npm install webpack@^%webpack_version%

test_script:
  - node --version
  - npm --version
  - cmd: npm run appveyor:%job_part%

Closes #54

[sapegin]

Do we need someone else’s review or I can merge it?

[bebraw]

@d3viant0ne Do you have any changes in mind for this? I don't understand Appveyor well enough to comment.

[joshwiens]

I wanted to try this config out in a project before I merged it, to make sure it works the way I think it should.

[michael-ciniawsky]

7 => 8 :)

[joshwiens]

@michael-ciniawsky - Now configured to use the config for it's nodejs versions like the travis template.

[michael-ciniawsky]

👍