build node-sqlite3 for node-webkit v0.8.6

Idea's the same as `?branch=master` in the URL of Tracis CI badge:
bystanders should not be scared by failures in experimental branches.

remove separate package version badge

count downloads of the npm package

fix db opening error with absolute path on windows

fix SQLITE_CANTOPEN error when cached.Database is called with absolute path on windows
use path.resolve for getting absolute path

update bundled libsqlite3 from 3080200 -> 3080403

update node-webkit building instructions to reflect new, simplified usage via node-pre-gyp - refs #261