Appveyor setup

Need to change the `project_id` in `appveyor.yml` and badge url in Readme . If there is an interest in switching to `node-pre-gyp` for the binaries, i can pitch in a separate PR for it :)

@nschonni 
Updating Node on Appveyor takes an awful lot of time & I suppose it doesn't matter here if we're testing on Node 0.10.28 or 0.10.29. I'd advise to use the following pattern:
https://github.com/mzgol/check-dependencies/blob/6519b54cad6f8f4142947b5ec4efe46b0803fdef/appveyor.yml#L16
In this way, if the major & minor numbers match, the update is not performed.