build node-sqlite3 for node-webkit v0.8.6

The code from mapbox/node-pre-gyp#79 is used to ignore RANDR errors. Line 40 in `package.json` is intentionally left blank to introduce “something's wrong” feeling (a commit hash should be replaced by a newer node-pre-gyp package version eventually).

Node-webkit's README now points to another hosting of the distributives, and that's what used for downloading.

A build for the newest node-webkit (v0.8.6) is [successful](https://travis-ci.org/mapbox/node-sqlite3/jobs/25039290).