Add basic Appveyor support

[![Build status](https://ci.appveyor.com/api/projects/status/yvwbs3qdkydil43l?svg=true)](https://ci.appveyor.com/project/simi/broccoli)
```
[ryba@retro  broccoli (win-ci *)]❤ npm test

> broccoli@0.13.1 pretest /opt/ryba/broccoli
> jshint lib test

lib/builder.js: line 10, col 2, Unnecessary semicolon.

1 error
npm ERR! Test failed.  See above for more details.
npm ERR! not ok code 0
[ryba@retro  broccoli (win-ci *)]❤ echo $?
1
```